A complex, multifarious problem or situation that cannot be solved easily and rapidly.
Any of several small freshwater polyps of the genus Hydra and related genera, having a naked cylindrical body and an oral opening surrounded by tentacles.
A dragon-like creature with many heads and the ability to regrow them when maimed.
A difficulty that has to be resolved or dealt with.
A puzzling circumstance.
A set of moves required to complete a climb.
A question to be answered, schoolwork exercise.
Objection.
Difficulty in accepting or understanding or refusal to accept or understand.
Causing a problem; problematic; troublesome.
Difficult to train or guide; unruly.