ratting

from The Century Dictionary.

• noun The act of deserting one's principles, and going over to the opposite party.
• noun In the trades, the act of working for less than established or demanded prices, or of refusing to strike, or of taking the place of a striker.
• noun A low sport consisting in setting a dog upon a number of rats confined in a tub, cage, or pit, to see how many he will kill in a given time.

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

• noun The conduct or practices of one who rats. See rat, v. i., 1.
• noun The low sport of setting a dog upon rats confined in a pit to see how many he will kill in a given time.

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

• verb Present participle of rat.
• noun archaic The sport of setting a dog upon rats confined in a pit to see how many he will kill in a given time.

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

• noun to furnish incriminating evidence to an officer of the law (usually in return for favors)