UNFAITHFULLY
unfaithfully, undependably, unreliably
(adverb) in an unfaithful undependable unreliable manner
Source: WordNet® 3.1
Etymology
Adverb
unfaithfully (comparative more unfaithfully, superlative most unfaithfully)
In an unfaithful manner.
Source: Wiktionary
UNFAITHFUL
Un*faith"ful, a.
1. Not faithful; not observant of promises, vows, allegiance, or
duty; violating trust or confidence; treacherous; perfidious; as, an
unfaithful subject; an unfaithful agent or servant.
My feet, through wine, unfaithful to their weight. Pope.
His honor rooted in dishonor stood, And faith unfaithful kept him
falsely true. Tennyson.
2. Not possessing faith; infidel. [R.] Milton.
– Un*faith"ful*ly, adv.
– Un*faith"ful*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition