toplevel -> top-level. It's spelled top-level elsewhere in the document

goblins/scribblings/api.scrbl

@@ -351,7 +351,7 @@ bootstrap an actormap with some interesting actors.
 Actors then operate on @deftech[#:key "turn"]{turns}, which are
 basically a top-level invocation; the core operation for that is
 @racket[actormap-turn].
-This can be thought of as like a toplevel invocation of a procedure at
+This can be thought of as like a top-level invocation of a procedure at
 a REPL: the procedure called may create other objects, instantiate and
 call other procedures, etc, but (unless some portion of computation
 goes into an infinite loop) will eventually return to the REPL with