A joke that is lame or that one cracks in a lame fashion. Lame cracks can also be a stupid try hard voice or expression. Usually lame cracks are initiated when the cracker is feeling insecure or nervous. The only one who laughs at a lame crack is the cracker. (adapted from 'wise crack')
Jimmy: Hey man I watched Everybody Loves Raymond last night an it was full of lame cracks.