http://words.bighugelabs.com/api/2/apikey
.. will bring up this sort of response:
http://words.bighugelabs.com/api/2/apikey/happy/
adjective|syn|felicitous adjective|syn|glad adjective|syn|well-chosen adjective|ant|unhappy adjective|rel|felicitous adjective|rel|glad adjective|rel|cheerful adjective|rel|content adjective|rel|contented adjective|rel|elated adjective|rel|euphoric adjective|rel|joyful adjective|rel|joyous adjective|sim|felicitous adjective|sim|blessed adjective|sim|blissful adjective|sim|bright adjective|sim|fortunate adjective|sim|golden adjective|sim|halcyon adjective|sim|laughing adjective|sim|prosperous adjective|sim|riant adjective|sim|willing