American Heritage Dictionary said:
cheat
VERB:
cheat·ed , cheat·ing , cheats
VERB:
tr.
To deceive by trickery; swindle: cheated customers by overcharging them for purchases.
To deprive by trickery; defraud: cheated them of their land.
To mislead; fool: illusions that cheat the eye.
To elude; escape: cheat death.
VERB:
intr.
To act dishonestly; practice fraud.
To violate rules deliberately, as in a game: was accused of cheating at cards.
Informal To be sexually unfaithful: cheat on a spouse.
NOUN:
An act of cheating; a fraud or swindle.
One who cheats; a swindler.
Law Fraudulent acquisition of another's property.
Botany An annual European species of brome grass (Bromus secalinus) widely naturalized in temperate regions.
Reloading is a deliberate violation of the rules of the game, ergo, by definition, it IS cheating. Even if nowhere in the manual does it say "thou shalt not reload", it is an obvious violation of the spirit of a fair game. for example, If you reload after losing a 90% battle because you
should have won, do you also reload after winning a 10% battle because you should have lost? Nobody? Didn't think so. So it's an unfair advantage, it's cheating, no big deal.
The question is not one of ethics, it's not wrong to cheat the AI, it doesn't make you a bad person or a bad civ player even; but you're deluding yourself if you think it's not cheating just because there's no human opponent. It's like playing solitaire while looking under all the cards to see which moves benefit you most in the long haul. No opponent, not wrong or bad, still cheating. Single player or multi, rules are rules.
You can justify it to yourself by saying it's for learining purposes, but be honest with yourself, you're still cheating in the specific game you're reloading.
Like others have said, it's your game, do as you will. I'm not telling anyone not to cheat, heck, i cheat, I'll reload if i want to try another path after i fail, but i consider those games losses and in the rare event i finish one i'll delete the replay so as not to pollute my high scores. I'll reload if i make a devastating mis-click like "will you accept cease fire" when i mean to click "what is the price for peace", i don't feel bad about that, i leave them in my high scores, i cheated. Living with the miss-click should be the price i pay for having a wireless mouse on my la-z-boy inxtead of having a stable surface and paying attention like i should. In multiplayer, it WOULD be the price i pay. In singleplayer, it's a victimless crime, so rock on, nobody's gonna call the cops.