Your team's side of the map, behind the inhibitors. "basing" means recalling to it, and a "base race" is both teams rushing the enemy nexus at once.
team chat
what you type
basing 5 sec
in full english
Basing, five seconds.
the context
"basing" replaces "b" for some players. "base race" is the endgame gamble: who destroys the nexus first.