Chicken-heart is a phrase that is often used to describe someone who is timid or lacks courage. If you're seeking synonyms for this phrase, you might want to consider words such as faint-hearted, gutless, spineless, yellow-bellied, cowardly, fearful, or timid. All of these phrases are synonymous with chicken-heart and can be used interchangeably to describe someone who is scared or unwilling to take risks. However, it's essential to keep in mind that these words can carry a negative connotation, so it's always wise to use them judiciously and in context.