noun

• A girl; also (by extension), a young woman.
  "Jenny Hill, a pale, overwrought, pretty Salvation lass of 18, comes in through the yard gate, leading Peter Shirley, a half hardened, half worn-out elderly man, weak with hunger."
• (especially Geordie, Wearside) A sweetheart.
  "But firſt him ſeemed fit, that vvounded Knight / To viſite, after this nights perillous paſſe, / And to ſalute him, if he vvere in plight, / And eke [also] that Lady his faire louely laſſe."
• (Northern England, Scotland) A female servant; a maid, a maidservant.
  "[…] I'll tell ye that after we are done wi' our supper, for it will may be no be sae weel to speak about it while that lang-lugged limmer o' a lass is gaun flisking in and out o' the room."
• (Scotland, familiar) A term of address for a woman, or a female animal.
  "As fair art thou, my bonie laſs, / So deep in luve am I; / And I will luve thee ſtill, my Dear, / Till a' the ſeas gang dry."