sissy
Most of the guys I hang out with want to know why he's being such a pantywaist about this.

SMART Vocabulary: related words and phrases

Cowardly
be afraid of your own shadowidiom
bottle
bottle out
chicken
chicken out
cravenness
fainthearted
gutless
lily-livered
pusillanimity
spinelessness
timid
timidity
timidly
timorous
unheroic
weak-kneed
wimp
wimp out
wimpy

You can also find related words, phrases, and synonyms in the topics:

Heroes and cowards
Weakness and vulnerability

pantywaistnoun[C] (CLOTHING)

old-fashioned
a piece of clothing that small children wore in the past, consisting of underwear that connects to the bottom of a shirt with buttons :
Little girls had to wear a panty-waist and bloomers, and in winter a petticoat.
The advantage of a pantywaist is that it provides a support on which to fasten the rest of the clothes.