Figure of speech like "not unlike"

• Toilets revolting; and that's an understatement
• Little child in stories making understatement
• Understatement for effect
• Literary understatement
• Figure of speech that employs ironic understatement
• Understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary)
• Ironical understatement

Wiktionary Word definitions in Wiktionary
n. (context rhetoric English) A figure of speech in which the speaker emphasizes the magnitude of a statement by denying its opposite; a figure of speech in which understatement is used with negation to express a positive attribute; a form of irony

Wikipedia Word definitions in Wikipedia
In rhetoric , litotes (, or ) is a figure of speech wherein understatement is used to emphasize a point by stating a negative to further affirm a positive, often incorporating double negatives for effect. For example, "She's not bad looking" could be used ...