What does ftl stand for in Battlestar Galactica?

FTL in almost any sci-fi setting stand for Faster Than Light. This typically refers to either travel (IE warp drive, hyperspace, space folding) or communication (IE subspace transmission). FTL is also commonly referred to as hyper-luminous or superluminal travel or communication.

In Battlestar Galactica they "spin up the FTL drive" as a form of charging or preparing the Faster Than Light travel capability of their ships. Although this process is never explained in detail, it is assumed that the FTL drives in BattleStar Galactica operate on a function of folding space to achieve FTL travel.