In the real world (the rest of the planet outside of the pool room), consider these examples.
A girlfriend, with a simple smile and wistful, appealing little-girl look easily drags you through the mall, store by store, by your nose. She knows how to shark.
Your sister's kid throws a temper tantrum when you say "No" – and you pretty much always give in. Hustled by a kid - tsk, tsk.
Your Mom says, "People are starving in Africa." You reluctantly force the boiled cabbage down your throat. Tricked! (And don’t try the “Let’s send it to them.”) By the way, all Moms are master gamesmanship tricksters and child manipulators.
The common element in all sharks is that your intention was to do one thing, and somehow you were manipulated into doing something else. Your friends, relatives, acquaintances, and co-workers use these mind games to push you in that person's preferred direction, regardless of any original intentions and plans.
By the way, skillful and knowledgeable pool playing, or a lucky roll is NOT sharking. It really is bad sportsmanship and poor manners to accuse anyone of sharking when they are simply better players.
Note: No scientific study has ever been done to determine just how common sharking is, in relationships, family, friendships, various sports, etc. It might be worth a Ph.D. to some enterprising college kid.
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