From WordNet (r) 2.0 (August 2003) [wn]:
princess
n : a female member of a royal family other than the queen
(especially the daughter of a sovereign)
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Princess \Prin"cess\, n. [F. princesse. See Prince, and cf.
Princesse.]
1. A female prince; a woman having sovereign power, or the
rank of a prince. --Dryden.
[1913 Webster]
So excellent a princess as the present queen.
--Swift.
[1913 Webster]
2. The daughter of a sovereign; a female member of a royal
family. --Shak.
[1913 Webster]
3. The consort of a prince; as, the princess of Wales.
[1913 Webster]
Princess royal, the eldest daughter of a sovereign.
[1913 Webster]