I am not trying to be pedantic, but the terms should be used properly, and there is a safety reason for this;
From Tacking (sailing) - Wikipedia, the free encyclopedia
Tacking or coming about is a sailing maneuver by which a sailing vessel (which is sailing approximately into the wind) turns its bow through the wind so that the direction from which the wind blows changes from one side to the other.
In preparation to tack, the helmsman should prepare the rest of the crew by calling "prepare to come about!" or "[make] ready about." To which the crew should respond *after* preforming what ever duty they need to do in order to tack, and ducking out of the way of the boom; "ready about." After the entire crew has indicated "ready [about]", the helmsman should state, as putting the wheel or tiller over, "hard to lee" (usually used with a tiller - the meaning is that they are pushing the tiller hard to leeward), or "coming about [now]" thus indicating that the boom will imminently be changing it's side.
This is different from gybing;
A jibe or gybe is a sailing maneuver where a sailing vessel reaching downwind turns its stern through the wind, such that the wind direction changes from one side of the boat to the other. For square-rigged ships, this maneuver is called wearing ship.
In preparation for a gybe, the helmsman should call "prepare to gybe." To which the crew should respond "ready [to gybe]" when they are, in fact, ready. This usually involves trimming the main, and preparing the jib sheets, and ducking. As the helmsman executes the maneuver, s/he should call "gybe ho" (salty), or "gybing" (lubberly). Again, this is a warning that the boom is imminently about to change sides, and it may be a sudden, violent, movement.
In general; gybing causes a much more sudden dramatic change in the boom's position, and therefore is more likely to cause serious injury.