Entry 1 sense Webster, 1913 Lumbago /ləm-bāg'-ōˌ/ · Lum·ba·go · IPA /ˌlʌmˈbeɪˌɡoʊ/ 01 n. A rheumatic pain in the loins and the small of the back. 1. A rheumatic pain in the loins and the small of the back.(Med.)