under the gun

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective idiomatic Under great pressure to perform.
• adjective poker Of, pertaining to, or in the situation of first player to act on the first round of betting.
• adjective obsolete, military Too close to be subject to artillery fire.
• adverb poker When in the situation of being the player who acts first in the first round of preflop betting.