A tankard is a large, heavy cup with a handle. You might swig root beer from a pewter tankard at a Renaissance festival.
Tankards are old fashioned mugs, rarely used today except as a novelty. Though they're almost always made of metal, occasionally tankards are wooden or ceramic. You might win an engraved silver-plated tankard as an award, or spy tankards in a movie during a rowdy pub scene. The word was first used in the 14th century, but it originally meant "large, tub-like vessel."