As with most people, your first experience with full-strength alcohol was likely a bad one. Perhaps you stole a sip of what was in grandpa's flask. Maybe you were at a party and decided to step outside your vodka-tonic comfort zone, only to instantly regret doing a shot of rum for macho points. Maybe you actually ordered a random bottle of single malt scotch only to have it sit for years on your shelf.
In any of these cases, you would probably not have described the experience as “smooth.” So what is "smooth," actually? Can we actually define it? The best I can say is that smooth means there's not a lot of hot alcohol burn on the palate, nor is there much of a burn as the alcohol makes its way down after a swallow.
On any given spirits forum, there is a person right at this very moment asking for the experts to recommend them a “smooth” whiskey, rum, or tequila. Their efforts are well-intentioned, but often it's a question that becomes nearly unanswerable. Here's why:
Your tastes change as a drinker
When I first tried Cutty Sark six years ago, I thought it was a borderline undrinkable “Grampa whisky.” A few months ago, giving it as fair of an appraisal as I could, I found it to be more complex than I remembered with some distinct lemon-ness. And you know what? While I remember Cutty tasting like rocket fuel back then, I found it certainly smooth enough today. To the point where it wasn't even on my list of good / bad evaluative criteria.
Eventually, your tastebuds become inured to the harshness of alcohol, just in the way that John McCain might have had an okay day or two in that hut.
As such, what bothers you now may not in the future. The same tends to hold true with peat, incidentally. At the beginning of your drinking career, everything seems smokey. Then that begins to fade. Two friends and I remarked recently that Talisker 10 seemed like the final boss of peat just a short while ago, and now it seems pleasantly well-balanced.
Additionally, "smooth" might just become a function of how used you are to a particular taste. If you only drink Grey Goose, it might be hard to find any rum or whiskey you'd consider smooth. All of the qualities that make one spirit different from another are accentuated and heightened when you're tasting something new for the first time.
Many things can be smooth
“Smooth” isn't necessarily something that can be charted in terms of either accessibility or price, which makes it even more odd. You can find a bottle of Glenfiddich 12 all over the planet, but I find it actually a little “hot” when compared to most other 12-year expressions. Alternately, Ballantine's Finest is dirt cheap, but I would wager that most would find it far more "smooth" than an Irish whiskey like Jameson.
Usually when people want something “smooth,” there's an implication that they're willing to pay for it. The good news is that you really don't have to. What you think is smooth will probably exist at a bewildering variety of price points and across a number of types of spirits.
Smooth isn't as concrete as you'd think
I would say that serious students of spirits are actually more interested in three criteria that supersede smoothness: Aroma, Taste, and Finish. Does it smell good? Does it taste good? Do we like the feeling it leaves us with after we swallow? A lot of people would argue that any spirit can be sacrificed on one of these three altars.
“Smooth” doesn't tell us much about anything, since it's used as an on/off switch and doesn't give an outsider any aperture into the experience of the taster. We can't ask “How smooth?” or even “What kind of smooth?” and hope for a good answer.
Smooth isn't just Referring to alcohol Content
Now this one is probably the most surprising. Usually when people are talking about smoothness, there's an implicit assumption that all alcohol tastes like a gulp of napalm. Therefore, wouldn't the best whiskey, gin, rum, or vodka be the one that tastes less like napalm? Logically, we might conclude that the lowest permissible ABV of 40% (if it's something worth drinking) would be the best.
But here's the strange thing: it ain't quite the case.
Some spirits are just flat-out hot. Cheap rum and bourbon always seems to coat the back of my throat in a very unpleasant, lingering burn. Oppositely, there are some cask strength whiskies bottled at more than 60% alcohol by volume that are a lot more pleasant to sip—assuming you take your time with them.
In general, more ABV translates to more flavor in the glass for you to do with what you'd like, but it's not really a linear relationship with how prickly, astringent, or warming something is at a specific percentage. Usually a 43% spirit will be “hotter” on the palate than a 40%, but not always!
Yeah yeah yeah, I didn't read any of that
Suppose both you and I have a vague idea of smoothness and you just want a blind recommendation with me knowing absolutely nothing about what you like, or what your dad likes, or what your friend likes so that you can have something good at his wedding, etc.
I would say you'll tick the largest number of boxes by buying a bottle of single-malt scotch, añejo tequila, aged rum, or Irish Whiskey costing between $50 and $70. And if you're buying whiskey, make sure it isn't peated.
There you go: smooth.