(1):

(a.) Resembling iron taste, hardness, or other physical property.

(2):

(n.) A sort of humor, ridicule, or light sarcasm, which adopts a mode of speech the meaning of which is contrary to the literal sense of the words.

(3):

(a.) Made or consisting of iron; partaking of iron; iron; as, irony chains; irony particles.

(4):

(n.) Dissimulation; ignorance feigned for the purpose of confounding or provoking an antagonist.