Claustrophobic (adjective)

1. Having a fear of closed or enclosed spaces.
2. Feeling uncomfortable or anxious in enclosed or cramped spaces.

Origin:

From the latin claustrum ("a closed place") and the greek φόβος (phóbos, "fear"). the term claustrophobic was first used in the 20th century to describe a fear of closed or enclosed spaces.

Examples:

1. He was feeling claustrophobic in the elevator.
2. She was claustrophobic and couldn't stand being in the small room.
3. The tunnel made him claustrophobic.
4. The claustrophobic feeling was overwhelming.
5. He was claustrophobic, so he avoided crowded places.