Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: social gathering 
Words: meeting, cinema, club, group, submarine
submarine

Category: outdoor sport activity 
Words: wrestle, fish, iguana, hiking, hunt
iguana

Category: personal characteristic 
Words: cool, icy, calm, persistent, unruffled

icy