add_filter( 'gettext', 'webplus_translate_woocommerce_strings', 999 );
function webplus_translate_woocommerce_strings( $translated ) {
    // Store all string in an array
    $translatedStrings = array(
        'Sale!' => 'ON OFFER',
        'Product Description' => 'Product Specifications',
    );
    $translated = str_ireplace( array_keys($translatedStrings), $translatedStrings, $translated );
    return $translated;
}