WordPress at a glance
action is not described

woocommerce_removed_coupon action-hook . WC 1.0

Usage

add_action( 'woocommerce_removed_coupon', 'action_function_name_2102' );
function action_function_name_2102( $coupon_code ){
	// action...
}
$coupon_code
-

Where the hook is called

WC_Cart::remove_coupon()
woocommerce_removed_coupon
woocommerce/includes/class-wc-cart.php 1845
do_action( 'woocommerce_removed_coupon', $coupon_code );

Where in WP core the hook is used WooCommerce

woocommerce/includes/class-wc-cart-session.php 52
add_action( 'woocommerce_removed_coupon', array( $this, 'set_session' ) );