Understatement

Noun

1. A figure of speech whereby something is made to seem smaller or less important than it actually is, either through phrasing or lack of emphasis, often for ironic effect.

   "A master of understatement"

2. An instance of such phrasing or lack of emphasis; an incomplete statement.

   "Now that's an understatement."

3. An incomplete disclosure that intentionally withholds relevant information.