@jackdaniel It is not, in any sense of the word. You cannot run a trivial (Common, Zeta, MAC, Inter ...) Lisp program in Scheme. The semantics are plenty different that I think, truly, that it is useful and even important to differentiate Scheme and Lisp (which is different from one being better or worse .. they are both nice languages!)
I sometimes troll that PHP is a C since .. for many trivial programs, you need to change less than between Scheme and Lisp.