adj. The type of search one conducts that leads to failure or disappointment.
Experienced with increasingly regularity on the interweb in the latter 1/2 of the oughties.
Archaic A phrase used to describe a brief, or not all that thourough a search.
See OED for more info.
2009 Dude #1: Did you finally call that chick?
2009 Dude #2: Nah, I made a cursory search.
2009 Chick #1: Did that dude ever call you?
2009 Chick #2: No. It appears ours was a cursory encounter.