How to Enable/Install Spell Checker in Firefox:
(1) Go to https://addons.mozilla.org/en-US/firefox/addon/3497
(2) Browse through the page and click add to Firefox.
(3) Software installation Dialog box will appear and click install.
(4) After installation completed, click restart Firefox.
In order to enable/disable spell check Right Click on the composing area and click spell checking to enable or disable it.
How to lookup for Definition:
(1) Go to https://addons.mozilla.org/en-US/firefox/addon/2083
(2) Browse through the page and click add to Firefox.
(3) Software installation Dialog box will appear and click install.
(4) After installation completed, click restart Firefox.
While composing select the word, right click on it and select “Inline Definitions” From popup menu. You will see the meaning of word.