First, a Tarotcentric definition:
sherlock, verb—to cold read or deductively assess a person’s nature or condition, or that of a situation, as Sherlock Holmes would often do, thus giving the impression some unusual or psychic power of perception is at work. He quickly sherlocked the woman, and told her some amazingly true things about herself.
noun—a person who employs these methods. That sherlock is pretending to use Tarot cards.
As Holmes would say, it is elementary. Of course it only appears so, because the trick is dependent upon a considerable amount of prior knowledge and understanding, used like a table of Tarot weapons to mimic magical acts.
In a recent NY Times movie review of Sherlock Holmes, the reviewer notes that Conan-Doyle was never much interested in fleshing out Holmes as a character, but hung characteristics about a vague form of a sleuth, and let people, and eventually movie-makers, fill in the gaps:
"Yet Holmes’s vagueness and incompleteness on the page are what make him so irresistible as a pop figure, on whom we can project our own interpretation. A lot of what we know, or think we know, about him—the deerstalker hat, the cloaks, the catchphrase “Elementary, my dear Watson”—comes not from the texts at all but from subsequent imaginings of him, the movies especially."
The thing is, the more we know, and especially the more we know and accept an authorized view, the less it seems we need or should bother with our imaginations, or our tendency to fill in gaps of meaning and signification. This strikes a lot of people as an innately bad thing, like an assault on their right to make up things which are not evidently indicated or called for. Thus knowledge, or authorized information, becomes an enemy.
Consider the game Monopoly, which might be more fun for children to play by making up rules, instead of learning them, but which is always a worse game for the additions and omissions. When I say "worse", I mean there is an elegant balance in the rules of the original, which is actually admirable and even beautiful. Changes, especially those designed to make the game less "mean" and ruthless—less brutal on children's self-esteem—make the game weaker and less interesting. The failure to learn the rules of the game leads to an almost antinomian hatred of them later by many adult players, who assume their fondly-recalled traditions are inherently superior to whatever silly rules were once written by some stupid game designer back in the day.
This is also the case with Tarot, which is widely revered as just the sort of vague and incomplete set of symbols on the card that people love to color with their ignorant projections. In fact, one of the many manifestations of people's ignorance and unwillingness to do anything effective about that (like read dreaded occult texts), is the proliferation of "theme" decks, mashups of cultural detritus with the always handy tarot-tabula-rasa. I had thought by now there would have been a Sherlock Holmes Tarot, in fact, but Amazon says nothing available.
Oh Stuart! Here boy! Fetch another crappy theme-deck.
Life is short, and I suppose learning the rules of an old board game like Monopoly, which you think you know anyway, or the rules to Tarot, an even older card game, which you are not even sure can be known authoritatively, seems absurd given that you cannot even muddle your way through the myriad rules of life under which people are increasingly being buried.
But, the truth and often the fruit of an effort to properly learn the terrific and terrible trifles, will never yield themselves if you are lazy and vain and vague.
And I would say obtaining the fruit of Tarot is a lot more interesting than obtaining the fruit, say, of learning how to obey the new rules for getting anally probed before boarding an airplane.
To each his own of course.