InteLib Lisp is a dialect of Lisp grown together with InteLib itself. Traditionally this dialect is what the library imitate with the default set of compile-time defines. However, having the interactive interpreter of the dialect (the interpreter is named NILL, which stands for iNteractive InteLib Lisp), we can say that InteLib Lisp is a real existing dialect of Lisp.
Some details about the dialect are here: http://www.intelib.org/libdocs/ill_lang.txt
Some C/C++ programmers can say that InteLibLisp is a kind of "Lisp for C programmers". For example, it has input/output functions similar to those from stdio.h; e.g. you can write
(let ((file (lfopen "data.txt" "r"))) (if file (progn (setq read_string (lfgets file)) (fclose file) )) )
Well, those lfopen, lfclose and lfgets do ring a bell, don't they? You see, even that "r" as a second parameter of lfopen is there.
Partly this is because the dialect was developed by a person who is a C programer himself.
See also: InteLibScheme