o.k. first to define some terms which seem to be misused a bit
a hack is something that the program was never intended to do for example a text editor being able to edit HTML or in a game a infantryman being able to walk through walls, or even the ability for non jet type units to do a high jump/fly.
a mod (non hack) would be enabling or changing something in game that is contained in original program i.e. using a higher than 10 mouse sensitivity, turning on mini map to always show enemies, or even loading custom avatar's.
a true wall hack enables a player to see and shoot through walls however i wont touch this subject any further
a cheat is something to give someone a unfair advantage.
so radar a cheat? maybe
radar a hack? nope
far as what sleep killer said on auto aim, if you use the native auto aim then no it is not a hack( can be disabled through no aim though ) if you make a auto aim to work in game via code caves(most likely the way you are thinking of) it is now dealing with new code therefore is a hack.
my opinion on this subject is yes as long as host permits so.
a hack is a modification, though a mod is not always a hack. would be the correct statement and i apologize if i have made anyone offended