squeal

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

• intransitive verb To give forth a loud shrill cry or sound.
• intransitive verb Slang To turn informer; betray an accomplice or secret.
• intransitive verb To utter or produce with a squeal.
• noun A loud, shrill cry or sound.

from The Century Dictionary.

• To utter a sharp, shrill cry, or a succession of such cries, as expressive of pain, fear, anger, impatience, eagerness, or the like.
• To turn informer; peach; “squeak.”
• noun A shrill, sharp cry, more or less prolonged.
• Infirm; weak.

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

• intransitive verb To cry with a sharp, shrill, prolonged sound, as certain animals do, indicating want, displeasure, or pain.
• intransitive verb Slang To turn informer; to betray a secret.
• noun A shrill, sharp, somewhat prolonged cry.

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

• noun A high-pitched sound, as a scream of a child, or noisy worn-down brake pads.
• verb To scream by making a shrill, prolonged sound.
• verb To give sensitive information about someone to a third party; to rat on someone.

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

• verb utter a high-pitched cry, characteristic of pigs
• noun a high-pitched howl
• verb confess to a punishable or reprehensible deed, usually under pressure