Drop is a term that has multiple meanings when used in land-based casinos, depending on the situation it is used in.
When used in blackjack, the term drop has the same meaning as fold. By folding in blackjack, you are basically taking the surrender option that allows you to drop your hand and keep half of your initial stake.
In addition, drop can also refer to the money lost by either a player or the casino.
Naturally, the meaning of the term depends on the context and the person using it, but since these two meanings are very different, there shouldn’t be any confusion.