Yes, that was in the dictionary too. I figured it was a little too arcane to include. I wasn't even sure about bothering to list the bolo knife.
I can't speak for anyone else but it designated two separate things in our organization:
APB had a more important rating than BOLO
BOLO was used as a more general term (we had dozens of BOLO or updated BOLO's every day)
APB was used to specify that it was a little more important and needed more attention
but that was just our dept.
I've heard some dept's decided to scrap both terms and goto a more logical sounding natural way of expressing the situation: BOLO sounds better and is easier to remember, so it was used instead of the APB
there was also the problem with giving the info over the radio and background noise/mixing it up with other terms.
This is NOT recent info- this is as per 2000 when I retired.
and my department has changed since then likely
you can see at this link:
http://forums.officer.com/t39148/
that it differs at different places
Wiki has some good info on it:
http://en.wikipedia.org/wiki/All-points_bulletin
again... it is part of the country, department, associations, the boss, local radio guidelines, etc.
hope that helps and answers the question.