Neither /\ nor \/ are defined as operators in the ISO C89 standard, and I don't think they were ever defined in any earlier version. And they are definitely not defined in C99 as far as I know.
Here's a draft of the ANSI C89 standard, for reference: http://flash-gordon.me.uk/ansi.c.txt
(You are likely a victim of some weird arcane preprocessor magic)
I don't believe I've ever seen those operators anywhere. Ever.
C has never had those operators.
Typically \/ would be an escape code in some string systems, not sure that /\ has ever had any meaning.
The Caret (^) performs a bitwise exclusive or.
I don't believe there is a "V" operator. That's the letter 'V' (or something that looks a whole heck of a lot like it). Somebody might want to name a variable that.
If you have spaces around them, then:
a /\ b ===> a / b
a \/ b ===> a / b
Logic: the preprocessing phase has to deal with backslash and a character after, and is quite likely to treat backslash-space as space, and backslash-slash as slash.
That said, both the SUN C compiler (version 12) and GNU C compiler (version 4.4) reject code containing the backslash. But I could easily believe that old, pre-standard C preprocessors were less careful about it.
The operators have never been part of an official version of C.
Also, the standard would not allow the interpretation I gave (section 5.1.1.2 Translation phases, in both C89 and C99) - but non-standard compilers are not constrained by the standard, of course.
Added after the source was posted:
Interesting! So it looks plausible for 'a = b /\ c;' to assign the maxiumum of b and c to a, and 'a = b \/ c;' to do the minimum (or, as Greg Hewgill pointed out, more likely vice versa). And, in those days, it was probable that the modern '+=' operators were still written as '=+' and were in fact two tokens (no supporting evidence for this assertion; failing memory again), so the hypothetical 'a =/\ b;' (or, in modern notation, 'a /\= b;') would have been the max-assignment operator, etc.
It also occurs to me that Thompson's ACM Turing Award speech 'Reflections On Trusting Trust' is somehow relevant.
I doubt they ever meant anything. If they ever did, it was a long time ago. The only major operators I know of that have been removed from C were =+ and =-, which were early synonyms for += and -=. You might want to look at DMR's Primeval C Page for evidence.
I'm not sure about \/, but /\ is a valid construct. It is used to place the two slashes of a single line comment on separate lines. For example:
/\
/ Comment content
This works because the backslash character escapes the newline and the parser continues as if it wasn't there. This will not work if there is a space after the backslash or if the second forward slash is indented. Because of this, it is possible to escape as many newlines as you like, as in
/\
\
\
\
\
/ Still a legal comment.
Backslashes can also be used at the end of regular single line comments to make them continue to the next line, as in
// Yet another comment \
This line is in the comment \\
And so is this one!
I'm going to guess that these are a reference to formal symbolic logic:
http://en.wikipedia.org/wiki/Table%5Fof%5Flogic%5Fsymbols
\/ is used to denote disjunction (OR) /\ is used (less frequently) to denote conjunction (AND)