pusillanimous

You can describe someone who lacks courage as pusillanimous, such as a pusillanimous student who is too afraid to speak out against someone who is bullying others.

Its Latin origin — pusillus and animus — tells us that pusillanimous means "very small spirit." If you are pusillanimous, pronounced "pew-sill-AN-ih-mus," you don't have the spirit — or the confidence or drive — to step up when it matters. The pusillanimous person stays quiet, doesn't get involved, waits for someone else to take a stand — not out of laziness, but out of fear.

Definitions of pusillanimous
1

adj lacking in courage and manly strength and resolution; contemptibly fearful

Synonyms:
poor-spirited, unmanly
cowardly, fearful
lacking courage; ignobly timid and faint-hearted