WordPress at a glance
action is not described

uninstall_(file) action-hook . WP 2.7.0

Fires in uninstall_plugin() once the plugin has been uninstalled.

The action concatenates the 'uninstall_' prefix with the basename of the plugin passed to uninstall_plugin() to create a dynamically-named action.

Usage

add_action( 'uninstall_(file)', 'action_function_name_3119' );
function action_function_name_3119(){
	// action...
}

Where the hook is called

uninstall_plugin()
wp-admin/includes/plugin.php 1054
do_action( "uninstall_{$file}" );

Where the hook is used (in WP core)

wp-admin/includes/plugin.php 1044
add_action( "uninstall_{$file}", $callable );