- a shrewd person, not easily moved
- a stubborn, hardheaded person
- any of various fishes; esp., a slender river minnow (Mylopharodon conocephalus) of central and N California
- A shrewd, tough person.
- A stubborn, unmovable person.
- pl. hardhead, or hard·heads Any of several fishes having a bony head, especially the Atlantic croaker.
- One who is practical or hardheaded.
- A brown diving duck, Aythya australis, native to Australia.
- Any of various freshwater cyprinid fishes of the genus Mylopharodon, or of saltwater sciaenid (Sciaenidae) fishes.
- Any of several weeds in or formerly classified in the genus Centaurea, particularly Russian knapweed (Acroptilon repens).
- (metallurgy) Residual ore that failed to melt during a smelting process.