litotes

English Thesaurus

1. understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary) (noun.communication)

hypernym	:	understatement,
definition	:	a statement that is restrained in ironic contrast to what might have been said (noun.communication)

hypernym	:	rhetorical device,
definition	:	a use of language that creates a literary effect (but often without regard for literal significance) (noun.communication)