Old coot is a derogatory term used to describe an old man who is seen as cranky, eccentric and grouchy. The term has been in use for centuries, but there are several synonyms available that can be used instead of it. Some common synonyms include grumpy old man, crotchety old man, grouchy old man, curmudgeon, codger and fogey. These words all describe an older man who is irritable, cantankerous, and often set in his ways. These synonyms can be used to describe an older person without the negative connotation associated with the term old coot.