According to the Grove Music Online the word arpeggio means: "The sounding of the notes of a chord in succession rather than simultaneously; also, especially in keyboard music, the breaking or spreading of a chord."[GroveMusicOnline]
In contemporary harp music it is standard practice to play all chords unbroken unless they are preceded by an arpeggio sign. The harpist will, however, break any chord that exceeds the span of his/her hand.
Chords and intervals are broken (arpeggiated) either upwards or downwards.
Breaking a chord gives it a warmer and somewhat fuller sound.
An arpeggio sign before the interval or the chord indicates that the chord is broken (arpeggiated). A harpist will always break the chord upwards unless the opposite is indicated. An arrow at the end of the arpeggio sign indicates the direction of the arpeggio. This arrow is unnecessary if all the chords in the composition are broken upwards.