[v] play a card lower than (a held high card)
[v] act (a role) with great restraint
\Un`der*play"\, v. i.
1. To play in a subordinate, or in an inferior manner; to underact a part.
2. (Card Playing) To play a low card when holding a high one, in the hope of a future advantage.
\Un"der*play`\, n. (Card Playing) The act of underplaying.