The Collaborative International Dictionary of English v.0.48:

Lass \Lass\ (l[.a]s), n. [OE. lasse; prob. of Celtic origin; cf.
   W. llodes girl, fem. of llawd lad. [root]123. See Lad a
   youth.]
   A young woman; a girl; a sweetheart.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lass
    n 1: a girl or young woman who is unmarried [syn: lass,
         lassie, young girl, jeune fille]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "lass":
   Dulcinea, Eve, Frau, babe, baby, best girl, broad, chick, colleen,
   cutie, dame, damoiselle, damsel, daughter of Eve, demoiselle,
   distaff, doll, domina, donna, dowager, dream girl, femme, filly,
   frail, frow, gal, gentlewoman, gill, girl, girl friend, girlie,
   heifer, hoyden, inamorata, jeune fille, jill, jo, junior miss,
   lady, lady friend, lady love, lassie, little missy, mademoiselle,
   maid, maiden, matron, milady, miss, missy, mistress, mouse,
   nymphet, old lady, piece, quail, romp, schoolgirl, schoolmaid,
   schoolmiss, skirt, slip, squaw, subdeb, subdebutante, subteen,
   subteener, teenybopper, tomato, tomboy, virgin, vrouw, wahine,
   weaker vessel, wench, woman, young creature, young thing



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

LASS
       Local Area Signaling Service