A chord that contains three notes, each two whole steps apart. It's identical to the major triad except that the fifth is raised a semitone.
For example: -
C+ contains the notes C E G#
- Bb+ contains the notes Bb D F#
- G+ contains the notes G B D#
- F+ contains the notes F A C#
One of the most interesting things about the augmented triad (besides the fact that it sounds so discordant) is that it is symmetric, because the intervals are the same between every note. This means that C+ is the same as E+ and G#+, because all three contain the notes C, E and G#. In fact, there are only four distinct augmented chords, and all of them are listed above.
The augmented chord doesn't exist in diatonic music. Because of the way the difference tones are, there's no audible tonal center to the chord, and it just sounds somewhat out of place. As far as notation goes, an augmented triad is denoted by a + in front of the "root" of the chord. When adding a seventh on top of an augmented triad, it's customary to write the quality of the seventh, followed by +5 (denoting the raised fifth). For example, G B D# F# comprises a Gmaj7+5 chord, while G B D# F comprises a G7+5 chord. | 
