secondary sex characteristic

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various physical characteristics that appear in humans at puberty and in sexually mature animals and that differentiate between the sexes without having a direct reproductive function.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A feature that distinguishes the two sexes of a species, but is not directly part of the reproductive system.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the genetically determined sex characteristics that are not functionally necessary for reproduction (pitch of the voice and body hair and musculature)