What does float do?

If 'FLOAT' lets a unit ignore a 'MAP EFFECT', that probably includes TRAPS...

There's a map that has a magic trap on certain floor, 'FIRE' spell is cast on whoever stays on top of it.

I forgot which specific map it is. It's the one with IRON GIANT at the center, and you have to step on two red button at the same time.

Basically, Float lets a unit ignore "max effect". There has been no map effect in the game (even on the JP server) so far.