unstable angina

[ŭn-stābəl]
n.
  1. Angina pectoris characterized by pain of coronary origin that occurs in response to less exercise or other stimuli than usually required to produce pain.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.