With an appearance of truth or trustworthiness; plausibly; reasonably. Now rare.

In a feigned or specious manner; colourably.

In a specious manner; attractively or plausibly, but deceptively or fallaciously.

Convincingly, believably; with an appearance of truth or trustworthiness; in a way that seems true or right; (formerly) spec. speciously.

So as to present an attractive appearance; with grandeur; beautifully, finely, splendidly. Formerly also in a negative sense: †in a deceptively…