(idiomatic) Immensely.

Eye dialect spelling of back at you.

Pronunciation spelling of back at you.

Alternative form of cosmic gravitational-wave background

Ellipsis of cosmic gravitational-wave background.

Alternative form of gravitational wave background

The stochastic background of gravitational waves produced during the creation of the universe. / The irresolvable diffuse background resulting from the mixture of weak gravitational waves of all sources.

Third-person singular simple present indicative form of shrink back

(informal, UK) Emphatic form of fed up: very frustrated, annoyed, tired.

(African-American Vernacular and gay slang) To make a witty or sarcastic retort.