Antanaclasis is a type of pun in which a word is repeated, and with each repetition it's context shifts from one meaning to another.
An example from Shakespeare:
O, cursed be the hand that made these holes!
Cursed be the heart that had the heart to do it!
Cursed be the blood that let his blood from hence!--Richard III, Act I, Scene ii, Lines 13-15
Both the second and third lines of the quote above make use of Antanaclasis with the repeated word 'heart' and 'blood'. Modern readers will find the first of these two easier to understand, but both of them are good examples with the meaning of the word being different the two times it occurs.
See also: