Specifically the wife of
叔叔 (shūshu, father's younger brother). Chinese kinship is precise:
伯母 (bómǔ, wife of father's elder brother),
婶 /
婶婶 /
婶子 (wife of father's younger brother),
舅妈 (jiùmā, wife of mother's brother),
姑妈 (gūmā, father's sister) — all 'aunt' in English. Also used as a friendly form of address (
李婶 'Aunt Li') for any older neighbor woman.