Longman Dictionary of Contemporary English - pins and needles

~ n 1 the uncomfortable prickly feeling you get in a part of your body when a full supply of blood comes back to it after having been partly blocked  (get pins and needles)  (If you sit like that for too long you'll get pins and needles.) 2 be on pins and needles AmE to be very nervous and unable to relax, especially because you are waiting for something important  (I wish Billy would give her a call. She's been on pins and needles all day.)