How to highlight all occurrences of a selected word in VIM?
In Normal mode:
:set hlsearch
Then search for a pattern with the command / in Normal mode, or <Ctrl>o followed by / in Insert mode. * in Normal mode will search for the next occurrence of the word under the cursor. The hlsearch option will highlight all of them if set. # will search for the previous occurrence of the word.
To remove the highlight of the previous search:
:nohlsearch
You might wish to map :nohlsearch<CR> to some convenient key.
The * key will highlight all occurrences of the word that is under the cursor.