1. a daughter of your brother or sister
The Collaborative International Dictionary of English v.0.48:
Niece \Niece\ (n[=e]s), n. [OE. nece, F. ni[`e]ce, LL. neptia,
for L. neptis a granddaughter, niece, akin to nepos. See
1. A relative, in general; especially, a descendant, whether
male or female; a granddaughter or a grandson. [Obs.] --B.
Jonson. Wyclif. Shak.
2. Especially: A daughter of one's brother or sister, or of
one's brother-in-law or sister-in-law. In modern English,
this is the primary meaning.
WordNet (r) 3.0 (2006):
n 1: a daughter of your brother or sister [ant: nephew]
Moby Thesaurus II by Grady Ward, 1.0:
43 Moby Thesaurus words for "niece":
aunt, auntie, blood brother, brethren, brother, bub, bubba, bud,
buddy, country cousin, cousin, cousin once removed,
cousin twice removed, daughter, father, first cousin,
foster brother, frater, grandnephew, grandniece, granduncle,
great-aunt, great-uncle, half brother, kid brother, mother, nephew,
nuncle, nunks, nunky, second cousin, sis, sissy, sister,
sister-german, sistern, son, stepbrother, stepsister, unc, uncle,
uncs, uterine brother
Bouvier's Law Dictionary, Revised 6th Ed (1856):
NIECE, domestic relations: The daughter of a person's brother or sister.
Amb. 514; 1 Jacob's Ch. R. 207.