I'm a hack. For sure.
My musical training is a few years of piano when I was kid, a few years of classical (think Segovia) guitar when I was a teenager, and ten years of off and on bedroom playing with crappy electric bass guitar equipment; I took a few music classes too that I barely attended or paid much attention to.
I can read music at the 2nd grade level, at best.
I have no idea what chords or scales I'm playing when I improvise something that works.
But I know what sounds good to me (I'm partially comparing the bassists I love listening to to the 'original' stuff I come up with coupled with the 'copy cat' stuff I practice to build up my chops to sound as good as those guys/gals).
Over the last 5 years I've acquired an outstanding bass and amp, and some decent recording equipment.
And I have practiced a bit each week to slowly improve my chops (mechanical skill as a bassist, whatever that means).
I've performed on stage and totally improvised weird and rhythmic stuff to the delight of onlookers (nobody said I sucked, even when I pushed them to tell me the truth). Sure it wasn't Ynqwie Malmsteen or Segovia quality string lickin', but it was interesting, unpredictable, and just plain sounded cool.
I totally hacked it up, and it was good.
So, to me, a hack is someone that doesn't know what they are doing, but tries to do it anyway.
Sometimes they sound good, sometimes they sound like crap.
I've heard very well accomplished musicians that know their theory, can sight read, can play around a pocket like any pro out there, and still sound like absolute crap because all they know is theory, and sight reading, and playing to the pocket.
It reminds me of sparring with 'black belts' back in martial arts classes years ago. I was a lowly yellow belt, and managed to score point after point on (some) black belts because; although they had the skill and knowledge to wipe the floor with me, they lacked the creativity to overcome my improvisation, and yes, straight up hackneyed style. I remember my instructor telling me I did it all wrong, but was still impressed with my ability to overcome skill with creativity.
So I'm with Scott here, I'm a hack, and I'm ok with it.
For comparison, my brother is a professional saxophone and other woodwinds player. He has a degree, plays with other professionals in studio and on stage, teaches, and makes 100% of his rather decent income as a musician. He knows what he is doing, and has worked very hard to get where he is.
He is most certainly NOT a hack.