Do you want a completely free offline dictionary? I have earlier posted about an online dictionary from Oxford (You can read here: Oxford Online Dictionary ). Here I will mention about a great free offline dictionary. Word web is free offline web dictionary with definitions and synonyms with more than 150,000 root words, related words, and 120,000 synonyms, 5000 audio pronounications, 65,000 text pronunciations and many more.
Even though Word Web completely works offline, you can use to check synonyms from Wikipedia if you connected to internet through Word web. Word web is spam free freeware and has full dictionary and thesaurus like US, UK, Indian, and global English.
You can download and install this freeware and use the benefits in day to day life. I would recommend you this freeware since it’s really worth and more over its absolutely free.
Download: Word web download.