The problem is that "render" is not a native bash command and there are no programs in the directory called render.
The solution is to find the ".bash_profile" file or the Mac OS X equivalent of this file (I use Linux, so I can't help with what its called) and add this line:
PATH is where the binary for the renderer is. Sorry I can't help with the path, but I only have Maya 6.5 and its on a Windows computer.
When this works, bash would know that render is just an alias for eg. /usr/maya/bin/render.bin
Hope this helps!
C. P. U. Its not a big processor... Its a series of pipes!