I wrote a piece containing the following six string guitar chord (fingering shown; first finger barre; standard tuning):
What is the name of this chord?
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A chord with those five pitches is a Gmaj7(#11).
A major-seventh chord has a root, major-third, perfect-fifth and a major-seventh. So, a Gmaj7 chord has the notes G, B, D and F#. The fifth (D) would often be left out of this chord, without affecting the overall sound much, or the naming of this chord type. This article about extended (tertian) chords points out that,
when it is not altered, the fifth is often omitted
The A and C# are extensions to this major-seventh chord; they are a major-ninth (9th) and augmented-eleventh (#11th) respectively. These kind of chords are described in terms of tertian harmony (where thirds are stacked on top of each other). As the 11th is the highest extension it implies the ninth.
However, it would also be valid to call this chord Gmaj9(#11); in this case Gmaj9 means a major-seventh chord with a ninth. This might be better, as it makes it explicit that you want a ninth. Although a ninth should be implicit in an 11th chord (otherwise it is some kind of add11 chord), there are sources which state that ninths can be left out of 11th chords, so Gmaj9(#11) would be a "fuller" description of your chord, even if not entirely necessary.