Best defensive Tyranitar moveset?

Since they are almost done with the defender tier list (and rating movesets is already done on a few pokemon) i would suggest to wait a little longer and wait till gamepress finishes the job.

Well it is even if tyra is à poor defender. Fb could be an option since it covers some of tyra s weaknesses.
But again There is nothing to Be afraid of if you encounter that mons. A simple aquali just destroys him

Tyranitars attack types are: dark, steel, rock, fire,

on the top of my head what i would use against a tyranitar:

MaChamp resist dark and rock, the rest +/-0. All attackts are fighting and steel (x1,95 and x1,25 attackbonus).

Primeape resist dark and dock the rest +/-0. All attackts are fighting (x1,95 attackbonus)

Mabye ursaring and ofc vapoeron.

Its movepool imo makes it weak in defending and i wouldnt use it that way. but if i guess; iron tail and fb (due to best option against fighters i think).

However, its is still like using a blissey with ZH+DG as an attacker.

Out of Tyranitar's moves, I'd say, yes. Iron tail+Crunch is his best defender set. Iron tail has more damage vs Bite considering the attack intervals of AIs. Crunch is a 3-bar charge move that would be used by AI more often than the other 2 charge moves.

In my experience, once the AI uses a single bar move, I don't need to worry about another so I use my own charge move without hesitation. But with 2 or 3-bar charge moves, there's always that chance of the AI using them consecutively and hit me while I'm using my charge move. 100% of a 70 base damage crunch is greater than 10% of stone edge/fireblast.

This is why Snorlax BS is a better defender than HB...IMO. Same rule generally applies to other pokemon.