/**
* @snippet Translate a String in WooCommerce
* @how-to Get CustomizeWoo.com FREE
* @author Rodolfo Melogli
* @compatible WooCommerce 3.7
* @donate $9 https://businessbloomer.com/bloomer-armada/
*/

add_filter( 'gettext', 'bbloomer_translate_woocommerce_strings', 999, 3 );

function bbloomer_translate_woocommerce_strings( $translated, $untranslated, $domain ) {

if ( ! is_admin() && 'woocommerce' === $domain ) {

switch ( $translated) {

case 'Sale!' :

$translated = 'On Offer';
break;

case 'Ajouter au panier' :

$translated = 'Choisir';
break;

// ETC

}

}

return $translated;

}