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.
An obstacle, delay, disadvantage, blow (an adverse event which retards or prevents progress towards a desired outcome)
An offset to the temperature setting of a thermostat to cover a period when more or less heating is required than usual.
A step-like recession in a wall.
The required distance between a structure and a road.