what is /usr/share/dict used for
The origins go way back as a place holder for the dictionary words used by the spell utility. spell is not available but the program look will use the words dictionary. You could use one of these alias/function courteous of Wilfredo Sanchez Jr. to do word look ups.

For ksh, zsh, and bash 

word () { grep -F -i "$*" /usr/share/dict/web2 ; }


For tcsh

alias word  'grep \!* /usr/share/dict/web2'