Wiktionary
n. (context idiomatic English) A prank in which a gullible victim is sent off on a fruitless search for a nonexistent item. vb. (context intransitive English) To participate, as the gullible victim, in a ''snipe hunt''.
WordNet
n. an elaborate practical joke in which the unsuspecting victim hunts a snipe and is typically left in the dark holding a bag and waiting for the snipe to run into it; "in the South a snipe hunt is practically a rite of passage"
Wikipedia
A snipe hunt or fool's errand is a type of practical joke that involves experienced people making fun of credulous newcomers by giving them an impossible or imaginary task. The snipe hunt may be assigned to a target as part of a process of hazing, but the word "sniper" is derived from a marksman with enough skill to shoot one.
A snipe hunt is a specific type of "wild-goose chase", where a person embarks on an impossible search. Where a wild-goose chase may be accidental, a snipe hunt is always initiated by a second person, as a prank.
It should also be noted that snipe do in fact exist, and they can be, and are hunted for sport. While the term 'Snipe Hunt' is most commonly used as described above, snipe hunting is a real pursuit.
Usage examples of "snipe hunt".
Then should I file 'wild-goose chase' under the same classification as the ~snipe hunt' Commander Riker had me engage in while we were at Starbase Twelve?
Data's snipe hunt must have gone well, because he saw Riker cover his mouth in order to stifle a laugh.
Grab a croaker sack and they'll take you on a snipe hunt too, if you favor snipe.
But at one camp, when Robin was feeling particularly bored, she took Chris on a snipe hunt.
For a man who never dirtied his own backyard, he showed remarkably little demur against going on a deadly snipe hunt for Alejandro.
And I'm not going down to the station to wait around like a boy playing snipe hunt.