v. 打老鼠；捕老鼠；背叛；告密（rat的ing形式）

[ noun ]
to furnish incriminating evidence to an officer of the law (usually in return for favors)
<noun.communication>

Rat \Rat\, v. i. [imp. & p. p. {Ratted}; p. pr. & vb. n.
{Ratting}.]
1. In English politics, to desert one's party from interested
motives; to forsake one's associates for one's own
advantage; in the trades, to work for less wages, or on
other conditions, than those established by a trades
union.

Coleridge . . . incurred the reproach of having
ratted, solely by his inability to follow the
friends of his early days. --De Quincey.

2. To catch or kill rats.

2. To be an informer (against an associate); to inform (on an
associate); to squeal; -- used commonly in the phrase to
rat on.
[PJC]


Ratting \Rat"ting\ (r[a^]t"t[i^]ng), n.
1. The conduct or practices of one who rats. See {Rat}, v.
i., 1. --Sydney Smith.

2. The low sport of setting a dog upon rats confined in a pit
to see how many he will kill in a given time.