According to Wikipedia, "in mathematical logic and computer science the symbol has taken the name turnstile because of its resemblance to a typical turnstile if viewed from above. It is also referred to as tee and is often read as "yields" or "proves"." The symbol itself looks like a letter t on its side, similar to a left-pointing, straight arrowhead (sec. 158) Would it be possible to use that arrow symbol (with a short one-cell shaft) to represent your symbol? You would have to define its use, of course.