Unsarcastic means sincere, genuine, and without irony or mockery. Its antonyms, on the other hand, include insincere, hypocritical, false, deceitful, and ironic. Insincere refers to someone who is pretending or not telling the truth, while hypocritical means saying one thing and doing another. False means not true or genuine, and deceitful refers to someone who is intentionally misleading or deceptive. Irony, the opposite of unsarcastic, involves saying one thing but meaning something entirely different. Using these antonyms for unsarcastic can help convey a different tone or emotion in speech or writing.