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 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.
• noun A bicycle for five riders; a quintet.

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