Definition of "distich"

Through these distichs of increasing intensity and vagueness, the reader is brought to the riddle of the concluding distich: as far as the speaker is concerned, the girl was ‘pure’, but she will not be if Aeschylus wants to receive the same service on a ‘bad condition’.

2012, Christer Henriksén, A Commentary on Martial, Epigrams Book 9, OUP Oxford, page 282