Traditionally mathematical operators are either prefix, postfix or infix. All the three forms of notation are equivalent and can be converted from one to another.
Formal systems such as programming languages usually enforce a certain fixity. Most languages are infix, LISP and its derivatives are prefix and concatenative languages are usually postfix.
If a formal system allows an operator to be used as either prefix, postfix or infix depending upon its position relative to its operands, how would you describe its fixity?
I was thinking along the lines of "unfix" or "nofix", but I'm not sure which one would be appropriate. I believe "nofix" is more accurate. Unfortunately there's no such word. On the other hand "unfix" means "to unfasten" or "loosen". Clearly not very accurate.