Cowardice is a trait wherein fear and excess self-concern override what is socially deemed as right and courageous—it is the opposite of courage. As a label, "cowardice" indicates a perceived failure to show enough mental robustness and courage in the face of a challenge.
Under many military codes of justice, cowardice in combat is a crime punishable by death (e.g. shot at dawn). The term describes a personality trait which is seen as a negative characteristic and has been shunned and disdained (see norms) within most, if not all cultures, whilst courage, typically viewed as its direct opposite, is generally rewarded and encouraged.
Do not confuse with timid, which does not possess the abovementioned negative connotations. Timidity is closer to a general lack of self-confidence, and it is possible for a character to be a coward while lacking timidty (e.g.: c41).