An ironic and often insulting way to describe something that you expect to be large but is in fact incredibly small. Can be used when you startsaying gigantic and change mid sentence.
Girl: Wow that football player is gigantic-ally small.
Girl: Oh god your cock is so big! It is (has a look) gigantically small... Get away from me you loser.
Canteen lady: That soup ladel is gigantically small, wow it is so small isn't it?