Prefix + &
if you have
bind q killp
.tmux.conf, you can press
Prefix + q to kill the window too, only if there is only one panel in that window.
if you have multiple panes and want to kill the whole window at once use
killw instead of
killp in your config.
the default of Prefix above is Ctrl+b,
so to terminate window by default you can use Ctrl+b &