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.