Resilient; able to endure hardship or criticism, with no apparent adverse effects.

(idiomatic) Bad luck.

(idiomatic) Bad luck (often an unsympathetic retort to someone suffering misfortune)

(chiefly US, idiomatic) A choice or judgment which is difficult to make, especially one involving only two alternatives.

(idiomatic) The compassionate use of stringent disciplinary measures, to attempt to improve someone's behavior.

Alternative form of tough-love

(mathematics) A measure, expressed by a positive integer (with the exception of complete graphs), of the connectivity of a graph.

A person who is difficult to work with.

(informal) A person who can endure physical or mental hardship; a hardened, strong-willed person. / (informal) A hardy, resilient animal or plant.

simple past tense and past participle of tough out