An Asus chord is an abbreviated notation reference to a "major A suspended" musical chord. It refers to a chord where the third note of the pattern is omitted and replaced with another note in the scale. Suspended chords are used to create a feeling of dissonance and tension between the notes, and they are commonly used in jazz and folk music.
In music, a major chord is made up of three notes: the first (known as the root), third (major third), and fifth (perfect fifth) notes within a given scale. In the example of the A major chord, the notes that make up the A major chord are A (root), C# (major third), and E (perfect fifth).
In a suspended chord, the major third is omitted, and replaced with either a perfect 4th, or a major second note.
In the case of the A suspended chord, this would mean that the major third could be replaced with either a D note (perfect forth), or a B note (major second).
The notation of the Asus chord can be altered to signify which variety of the suspended chord is used. An Asus chord with the perfect forth can be written as "Asus4," and with the major second as "Asus2."