If you want to surprise your mom with a sweatshirt, but don't know her size, it might take an act of subterfuge, like going through her closet, to find it out. Subterfuge is the use of tricky actions to hide or get something.
It's pronounced "SUB-ter-fyooj." As a countable noun, a subterfuge is a tricky action or device: She employed a very clever subterfuge to get the information she needed. Subterfuge is from French, from Old French suterfuge, from Late Latin subterfugium, from Latin subterfugere "to escape," from subter "secretly, under" plus fugere "to flee."