Channel (macro channel)
Beginner
The gap between two big blocks, like an aisle, that wires must squeeze through.
Novice
The gap between two macros, or between a macro and the edge of the core. Wires to the macros’ pins have to pass through it, so it must be wide enough for them.
Expert
Sized from routing demand: pins on the facing edges, wires passing through, power straps that must cross, and any cells you allow there. Narrow channels are often blocked for placement so cells aren’t stranded without room to wire, or the macros are pushed together (abutted) to remove the channel.
Explained in Floorplanning (Design Flow).
See also: Macro (hard macro), Halo (keep-out margin), Congestion.