What does dogfish mean in shakespeare?

Answer 1

Shakespeare only uses the word once, in Henry VI Part 1 where Talbot says:

Pucelle or puzzel, dolphin or dogfish,

Your hearts I'll stamp out with my horse's heels,

And make a quagmire of your mingled brains.

A dogfish is an actual kind of fish, once extremely common in temperate coastal waters worldwide, now threatened by overfishing. Talbot is playing with the title of the Dauphin, the French Crown Prince, whose title translates as "dolphin". Talbot says he could be a dogfish for all he cares.

Answer 2

"Dogfish" is a perfectly normal modern English word, which refers to a number of different sharks found in temperate waters. It meant the same to Shakespeare, when he used it in Henry VI Part 1.