1. To act dishonestly; practice fraud.
2. To violate rules deliberately, as in a game
Enough said, mind you buying into the whole trophies and achievement nonsense is pretty stupid too in my opinion. It's just a cheap way of forcing the user to replay a short game and artificially enhance it's longevity, So they feel slightly less robbed when they find out they just spent £40 on a 4 hour long game. Just one step away from palette shifting a few sprites and speeding the game up.
If people want to use cheats offline (i.e not playing with/against someone who isn't) then fair enough, it isn't hurting anyone. If people want to use cheats to gain trophies, then also fair enough it isn't hurting anyone either but if someone really thinks the number of trophies they have is somehow cheapened by someone else who cheats and gets the same trophies? Yeah that person needs a life.