wimp
wimp1 /wɪmp/ 
noun [countable] informal
Don’t be such a wimp!
2. a man who is thin and physically weak
—wimpish, wimpy adjective
wimp2 verb
wimp out phrasal verb spoken
to not do something that you intended to do, because you do not feel brave enough, strong enough etc
SYN cop out
| I |
noun [countable] informal Date: 1900-2000
Origin: Perhaps from whimper
1. someone who has a weak character and is afraid to do something difficult or unpleasant:Origin: Perhaps from whimper
2. a man who is thin and physically weak
—wimpish, wimpy adjective
| II |
verbwimp out phrasal verb spoken
to not do something that you intended to do, because you do not feel brave enough, strong enough etc
SYN cop out