(telephony) An audible signal on a voice phone line that sounds more frequently than a standard busy signal, indicating that no transmission path to the called phone number is available.

(uncountable) Popular music without any deep meaning.

A nuclear plant which produces fissionable material from high-energy neutrons as a byproduct in excess of the amount it uses to operate.

(dated) To eat breakfast; to eat the first meal of the day after a night of not eating or to conclude any period of fasting by consuming food.

plural of fast Fourier transform

plural of fast busy signal

A small, fast boat designed with a long, narrow platform and a planing hull to enable it to reach high speeds.

plural of fast radio burst

(astronomy) A tight band of radio-frequency waves that lasts only a millisecond, which packs the energy of millions of years of Solar output.

(idiomatic) To fail to make any progress.