Meaning : Turn abruptly and face the other way, either physically or metaphorically.
Example :
He turned around to face his opponent.
My conscience told me to turn around before I made a mistake.
Synonyms : swing about, swing around
Meaning : Improve dramatically.
Example :
The new strategy turned around sales.
The tutor turned around my son's performance in math.
Meaning : Improve significantly. Go from bad to good.
Example :
Her performance in school picked up.
Synonyms : pick up
Meaning : Turning in an opposite direction or position.
Example :
The reversal of the image in the lens.
Synonyms : reversal