eleventh

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

• noun The ordinal number matching the number 11 in a series.
• noun One of 11 equal parts.

from The Century Dictionary.

• Next in order after the tenth: an ordinal number.
• Constituting one of eleven equal parts into which anything is divided: as, the eleventh part of fifty-five is five.
• noun One of eleven equal parts; the quotient of unity divided by eleven: as, five elevenths of fifty-five are twenty-five.
• noun In early English law, an eleventh part of the rents of the year, or of movables, or both, granted or levied by way of tax.
• noun In music:

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

• noun The quotient of a unit divided by eleven; one of eleven equal parts.
• noun (Mus.) The interval consisting of ten conjunct degrees; the interval made up of an octave and a fourth.
• adjective Next after the tenth.
• adjective Constituting one of eleven parts into which a thing is divided.
• adjective (Mus.) Of or pertaining to the interval of the octave and the fourth.

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

• adjective The ordinal form of the number eleven.
• noun The person or thing in the eleventh position.
• noun One of eleven equal parts of a whole.

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

• adjective coming next after the tenth and just before the twelfth in position
• noun position 11 in a countable series of things