Is temper a noun

Yes, the Word 'temper' is both a verb and a noun.

The noun 'temper' is a Word for a state of mind seen in terms of being angry or calm; a Word for the degree of hardness and elasticity of metal; a Word for a thing.

The noun form of the verb to temper is the gerund, tempering.

Related noun forms are temperance, temperature and temperament.