Final answer:
Mercutio's line is an example of a pun, a word play that highlights the double meaning of 'grave' in the context of his impending death in 'Romeo and Juliet'.
Step-by-step explanation:
The phrase "ask for me to morrow and you shall find me a grave man" spoken by Mercutio in Shakespeare's "Romeo and Juliet" is an example of a pun. Mercutio uses this figure of speech, which involves a play on words, after he has been wounded and is dying. The word 'grave' can mean serious or sober, which Mercutio no longer is due to his jovial personality, but it also refers to the fact that he will soon be dead, hence in a grave.