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.
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