Pigeon-hearted is often used as a synonym for cowardly or timid. However, there are other words that could also be used in its place. For instance, a person who is easily frightened or lacks courage could be described as chicken-hearted or faint-hearted. They could also be called spineless or wimpy. Alternatively, you could use words like apprehensive or nervous to describe someone who is afraid or anxious. There are also more poetic synonyms, such as lily-livered or yellow-bellied, which come from archaic expressions concerning the liver and bile. Ultimately, the choice of synonyms will depend on the context and tone of the message you want to convey.