This includes the constructing of bars/lines with:
words of double/triple meaning for humour or effect.
words that are not obviously recognisable as rhymes to one another when pronounced correctly yet may share assonance and there for can be used in place of standard rhymes structurally with in a verse.
Also multiple rhyme patterns within lines added for show effect and cohesion.
Wordplay is one of the technical areas that can be assessed when judging how technically skilled an rapper/MC is.
Pharaohe Monch,Big L,Big Pun, Eminem are some examples of MC's whose work can be particually rich in wordplay.