Your funny bone is the soft part of your elbow which gives you an uncomfortable feeling on your skin if it is hit.
[informal]
funny bone in British English
noun
the area near the elbow where the ulnar nerve is close to the surface of the skin: when it is struck, a sharp tingling sensation is experienced along the forearm and hand
Also called (US): crazy bone
funny bone in American English
1.
a place on the inner elbow where the ulnar nerve passes close to the surface: a sharp impact at this place causes a strange, tingling sensation in the arm
2.
inclination to laughter; (one's) risibilities
Word origin
from its reaction to impact, but prob. suggested also by its relation to the humerus (hence, “humorous”)
Examples of 'funny bone' in a sentence
funny bone
For some strange reason, that answer seemed to tickle his funny bone.