protected function _getUniqueWord(array $definitions, array $existingWords)
    {
        $definition = $this->_randomizer ? $this->_randomizer->getArrayValue($definitions) : $definitions[array_rand($definitions)];

        if (array_search($definition['word'], $existingWords) === false) {
            return $definition;
        }

        return $this->_getUniqueWord($definitions, $existingWords);
    }