Allrounders I think, anyway, should be classified in a few ways:
True allrounder: Could be picked in the side either for batting or bowling. Averages of 35+ with the bat and 35 or less with the ball. Bowls every innings. Can bat anywhere from 3-7. Example Kallis
Batting allrounder: Pick in the side for their batting. Can tie up an end if need be. Averages 35+ with the bat and probably more than 35 with the ball. Bowls when needed. Bats usually anywhere between 3-7. Example Symonds
Bowling allrounder: Picked in the side for their bowling. Can bat relatively well. Averages hopefully around 30 with the bat and less than 30 with the ball. Bowls every innings. Bats between 6-9. Example Vettori
Then we get into part timers who are picked solely on their batting and will occasionally bowl once every 2-3 tests to break a partnership or if a bowler goes down. Example Smith
True allrounder: Could be picked in the side either for batting or bowling. Averages of 35+ with the bat and 35 or less with the ball. Bowls every innings. Can bat anywhere from 3-7. Example Kallis
Batting allrounder: Pick in the side for their batting. Can tie up an end if need be. Averages 35+ with the bat and probably more than 35 with the ball. Bowls when needed. Bats usually anywhere between 3-7. Example Symonds
Bowling allrounder: Picked in the side for their bowling. Can bat relatively well. Averages hopefully around 30 with the bat and less than 30 with the ball. Bowls every innings. Bats between 6-9. Example Vettori
Then we get into part timers who are picked solely on their batting and will occasionally bowl once every 2-3 tests to break a partnership or if a bowler goes down. Example Smith