good for nothing
Entirely without value; of no use whatsoever. Hyphenated if used as a modifier before a noun. This junky old computer my dad gave me is good for nothing! That good-for-nothing son of mine has been doing nothing but lying on the couch for the past two months!
good-for-nothing
If you describe someone as good-for-nothing, you mean that they are lazy and irresponsible. Ruth's father was a rich, charming, but good-for-nothing man. He lived with his alcoholic mother and her good-for-nothing boyfriend in a trailer park. Note: You can also call a person a good-for-nothing. She called him `a lazy, deceitful good-for-nothing'.
good-for-nothing
1. mod. worthless. (Usually having to do with a person.) Let’s get rid of this good-for-nothing car right now.
2. n. a worthless person. (Also a rude term of address.) Tell the good-for-nothing to leave.