Parse and extract synonym data from a website
You're doing things the hard way.   By that I mean, why build a web crawler for this?   Is it a requirement that you only use thesaurus.com?   There are several quality thesaurus services out there with APIs that you could utilize.

I've never used any of them, but a quick web search and a bit of sifting results and these ones appear to be at the head of the thesaurus API ballgame.


Altervista Thesaurus:  Thesaurus is a web service providing search capability for synonyms in different languages.
The synonyms are retrieved from the thesauri dictionaries of OpenOffice according to the relevant licenses.
Big Huge Thesaurus: This site sports a very simple API for retrieving the synonyms for any word. You can access the API by making a GET request...


I also found another Stack Exchange post on the topic, which lists some more options:
https://webapps.stackexchange.com/questions/9156/database-of-english-synonyms

If thesaurus.com is absolutely a requirement, then you're doing the best you can.  You have to send the request, crawl the page, extract the information you want, and format it into something you can use.  

thesaurus.com does have an API, but from how they describe it, its difficult to get them to give you access.  You can read more about that here:

thesaurus.com API