In a wicked, sinful, or dishonest manner; abominably; treacherously. Obsolete.

iniquitously, treacherously.

Deceitfully, treacherously.

In a traitorous or treacherous manner; treacherously.

In a treacherous manner; by or with treachery.

Like, or in the manner of, a traitor; traitorously.

= treacherously, adv.

Traitorously.

in a treasonous manner.

In a treasonable manner. (Originally Scottish)

traitorously.