Good set for Mewtwo

[Ichimaru]

My current moveset for mewtwo is:
Recover
Barrier
Power up punch
Pyscho Cut
The item for him is Mewtwonite x.
I would like to know your opinion and how to get a better moveset and also how to make him indestructible and also what does STAB mean when your talking about a move in pokemon?

 

[CrazyElf]

what does STAB mean when your talking about a move in pokemon?

STAB is a very common abbreviation and term in competitive play. It stands for same-type attack bonus. Basically, it is a 50% boost to the power of an attack, whenever the attack is the same type as the Pokemon user. When STAB happens, it results in a 50% power boost to the attack.

Also, here is my Mewtwo (specifically Mega-Mewtwo Y) set:

Mewtwo @ Mewtwonite Y
Ability: Pressure >Insomnia
EVs: 252 Spa / 4 Spd / 252 Spe
Nature: Timid
- Psystrike
- Calm Mind
- Focus Blast
- Shadow Ball

Use this set specifically for a fast Special Sweeper. With these moves, Mewtwo can be powered up by Clam Mind, and sweep with a variety of coverage moves.

 

[FLCL]

Mewtwo @ Mewtwonite X
Ability: Pressure
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Bulk Up
- Drain Punch
- Rock Slide/Taunt
- Zen Headbutt

This set is pretty straight forward, Bulk Up to raise Atk and Def to make it more difficult for priority users to weaken it, Drain Punch for recovery, though Low Kick could be run if you want power over recovery. Rock Slide hits Flying types and Taunt can prevent status and Zen Headbutt because Zen Headbutt/Drain Punch gives Mewtwo neutral coverage.

 

[Hikki]

Same Type Attack Bonus.

Mewtwo @ Life Orb/Mewtwonie Y
Ability: Pressure
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Psystrike
- Calm Mind
- Fire Blast
- Focus Blast
Psystrike for those with weak defense and main STAB. Calm Mind to boost its high Special attack and special defense. Two blasts to beat many others in Ubers.