n.1 a woman or girl in relation to sons and other daughters of her parents.
2 a (often as a form of address) a close female friend or associate. b a female fellow member of a trade union, class, sect, or the human race.
3 a senior female nurse.
4 a member of a female religious order.
5 (attrib.) of the same type or design or origin etc. (sister ship; prose, the younger sister of verse).
Phrases and idioms:
sister german see GERMAN. sister-in-law (pl. sisters-in-law)
1. the sister of one's wife or husband.
2 the wife of one's brother.
3 the wife of one's brother-in-law. Sister of Mercy a member of an educational or charitable order of women, esp. that founded in Dublin in 1827. sister uterine see UTERINE.
Derivatives:
sisterless adj. sisterly adj. sisterliness n.
Etymology: ME sister (f. ON), suster etc. (repr. OE sweoster f. Gmc)