The definition of a sissy is a timid person or an an insulting term for an effeminate boy or man.(noun)
A man who is scared of everything and whose friends all make fun of him for being so timid is an example of someone who is a sissy.
See sissy in Webster's New World College Dictionary
noun pl. sissies
Origin: dim. of sis
See sissy in American Heritage Dictionary 4
noun pl. sis·sies
Origin: Diminutive of sis.
Learn more about sissy