quintuplet

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

• noun One of five offspring born in a single birth.
• noun A group or combination of five associated by common properties or behavior.

from The Century Dictionary.

• noun A bicycle for five riders; a quintet.
• noun A set of five, as of car-springs, etc.
• noun plural Five children born at a birth.
• noun In music, a group of five notes to be performed in the time of three, four, or six. Also quintole. Compare nonuplet, triplet, etc.

from the GNU version of the Collaborative International Dictionary of English.

• noun A collection or combination of five of a kind.
• noun Five children born in the same labor.
• noun (Mus.) A group of five connected notes; a turn of five notes.
• noun A cycle having five crank shafts and adapted for five riders, all of whom can assist in the propulsion.

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

• noun One of a group of five babies born from the same mother during the same birth.

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

• noun a set of five similar things considered as a unit
• noun one of five children born at the same time from the same pregnancy
• noun the cardinal number that is the sum of four and one