Mac ;9D and ;9C from alt-left and alt-right
If you are using the bash shell, add the following to your ~/.inputrc:
"\e[1;9C": forward-word
"\e[1;9D": backward-word
Press Ctrl-X, Ctrl-R or restart the shell to apply changes.
Note: Part of the escape sequences above, specifically the 1, I had to guess based on what Xterm uses.