How tightly filler sits inside the binder, judged by feel and confirmed by draw measurement. Some styles vary density deliberately along the cigar, leaving the foot slightly looser.
Why it matters
Density is the lever connecting rolling technique to draw, burn rate, and heat: a dense bunch runs hot and tight, a loose one burns fast and tunnels.
In context
"Feel that - firm at the head, easy at the foot. That is how it should sit."