When I hear the term "arpeggio", to me, it is much more specific than just a broken chord. A broken chord, obviously is any chord that isn't played as a block chord. This could mean anything from alternating pairs of notes to Alberti bass and everything in between. But when I hear the term "arpeggio", I don't just think of a broken chord but a very specific broken chord, where everything ascends or descends in order. Thus, I don't think of Alberti bass as being an "arpeggio" since it is Low, High, Middle, High, and not ascending or descending in order.
But, I have heard several music theorists and even analyses of Beethoven's symphonies that refer to arpeggios more in general as any broken chord whatsoever. I have problems with this definition. I will use specific musical examples whenever possible to illustrate different forms of broken chords.
First, I will show what is undoubtedly an arpeggio, and what I think of as the definition of an arpeggio.
As you can see, whenever I am asked "Hey, what is the definition of an arpeggio?", I would answer something along these lines:
Imagine that you have a chord. Now break up that chord into its individual notes. Now, put those notes in ascending or descending order. There, you have an arpeggio. You can add octave extensions obviously, have chordal arpeggios, or even have an "arpeggio of arpeggios" figuration, where on both the macro scale(all the chords) and the micro scale(each individual chord), an arpeggio forms. You can also have the arpeggio move back and forth. As long as each chord tone is reached in ascending or descending order within an area of a few notes and this continues throughout the figuration, you have an arpeggio.
But, as I said, quite a few music theorists use the term arpeggio to mean any broken chord. Here are a few more examples of what I would consider to just be broken chords, not arpeggios:
This is a form of broken chord that I mentioned right at the beginning of my post, Alberti bass. This is very close to the arpeggio I showed earlier in its form. Only difference is that it goes Low, High, Middle, High, instead of in ascending or descending order. The start of the melody here though is an arpeggio, for sure and for certain.
Here, before the triplets, you simply have 2 notes alternating within a single harmony with the exception of the second beat of measure 7(where the note in the middle voice simply repeats). This is very similar to Alberti bass, except, only 2 notes are involved. At the triplets, you have an ascending arpeggio.
This is a corner case, because it is debatable whether or not it is a broken chord at all, given that it is just octaves. However, if we treat octaves as a broken chord, than this certainly shouldn't be in the definition of an arpeggio.
So, does arpeggio really mean any form of broken chord? Or does it mean more specifically, a broken chord in ascending or descending order?