Ugly means "extremely unattractive." On Halloween, some people wear ugly masks as part of their scary costumes.
Anything that looks or feels quite unpleasant is ugly. The adjective ugly can describe the way something or someone looks, but it can also describe behavior or actions — the ugly scene your little brother made at the toy store when he didn't get what he wanted or the ugly breakup of a friendship. Remember that when ugly becomes uglier and ugliest, the y becomes an i.