Heatmap
Also said as Death map, Kill map
A map of a level coloured by how often something happened at each spot: where players died, walked, stopped or looked. It is telemetry you can see at a glance.
A count of 400 deaths tells you little. Four hundred deaths at the same corner tells you exactly what to fix, and a second map tells you whether you fixed it.
Say it
“Pull a death heatmap for the bridge level from the last 2,000 sessions. If it is one hot corner, move the turret back five metres, then pull the map again next week.”
Where you’ve seen it
Wired's 2007 piece on Halo 3 described Microsoft's test lab making maps of where players died so that Bungie could spot unfair spots. Valve went further and published death maps from Half-Life 2: Episode Two.
Not to be confused with minimap
A minimap is for the player, while they play. A heatmap is for the team, and is built from many players' sessions.