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: moral characteristic 
Words: frank, concise, bun, matter of fact, fortitude
bun

Category: physical property 
Words: obese, heavy, area, chunky, fat
heavy

Category: outdoor sport activity 
Words: iguana, wrestle, climbing, fish, canyoning

iguana