From,
http://stackoverflow.com/questions/2877371/definition-of-lisp-form

A lisp form is data that can be evaluated.
3
is a normal form.
(+ 3 4)
(if x y z)
are compound forms.  procedure and special (or syntax) respectively.
procedure: sees the evaluated arguments
special: arguments are not necessarily evaluated.

(3 4 1) is lisp data that can't be evaluated, so is not a form at all.