A remarkably useless expression used thus far probably only by one person in the world, utilized to allow for faster typing by the typist at the expense of completely failing to get the point across. Regularly tends to confuse all readers, who usually try to interpret it as some form of foreign emoticon. A few will almost correctly guess it as "at less than," which still makes next to no sense.
Used regularly by said person because it is apparently much easier than typing "at least", in case you hadn't figured out by now that that is what is being referred to.
Directly from a Facebook wall post
Former roommate: "I quoted you in my status!!! I figured I needed to @< ref the guy who always says it when I use it in my own status to mean the same exact thing. NO worries."