Maj. 7 is for a major triad with a major 7th added. "+" and "aug."
are the same thing: major triad with an augmented (sharp) 5th. "-" is a
Berklee shortcut for minor (minor third), "alt." means any an altered 5th
(b5 or #5)and any tension used should be altered, i.e. b9, #9, #11, b13.
"dim." and the circle are both for a diminished chord, which is Root, minor
3rd, b5. "Dim7" is a dimished 7th chord, which is root, minor 3rd, b5, and
*double flatted* 7th (which is the same as natural 6). A circle with a line
through it is an outdated version of minor 7 (b5). It is usually referred
to as "half diminished" in classical music circles. It is a minor triad
with a flatted 5th and a minor 7th. Note that it is similar to diminished,
but the 7th is a half-step different. A traingle is an ambiguous shortcut
to mean Major 7th, but some people use it as just major, therefore it is
ambiguous. Avoid the triangle and the "half-diminished" symbol, and those
are pretty standard. The "-" sign isn't as widely used, but is pretty
popular in jazz circles.
Mike "author of the paraplegiac minor scale" Crutcher