Brickwall Limiting Definition

[timbreman]

I "thought" I knew exactly what brickwall limiting was until out of curiousity I looked up a definition which stated:
"New digital processing options allow for true, realtime peak limiting, where the attack time can be zero."

I am confused by that...the attack time 0?
Is this the defining characteristic of Brickwall or did they mean to say the "ceiling" ?

[hummer]

attack time "0" means that the limiter has "lookahead" capabilities. meaning, it analyzes the audio signal and predictively attenuates, effectively achieving a zero attack-time. in contrast, an analog limiter can never achieve a zero attack because it reacts to the signal.

brickwall does, indeed, refer to the limiter's ability to keep the amplitude of the signal from exceeding the set output ceiling, which may or may not be 0 dBFS. but this is made possible by the "lookahead" feature.