The phrase "tiger heart" typically denotes courage, strength, and determination. However, its antonyms would include attributes like timidity, weakness, and surrender. A person with a "mouse heart," for instance, lacks the bravery and daring of a tiger-hearted person. Similarly, a "reconciliatory" heart might shy away from conflict, while a "faltering" heart might lack conviction or certainty. It's worth noting, however, that the opposite of tiger-heartedness need not necessarily be an unflattering quality or trait. After all, there are times when prudence, caution, and gentleness are called for, just as there are situations that require boldness and conviction.