Definition of lasses:
(n) :
A girl; also (by extension), a young woman.
(n) :
(Scotland, familiar) A term of address for a woman, or a female animal.
(n) :
(especially Geordie, Wearside) A sweetheart.
(n) :
(Northern England, Scotland) A female servant; a maid, a maidservant.
(n) :
(specifically) A female member of the Salvation Army; a hallelujah lass.