Nuke is an Army... generally you'll hear terms like "Full Nuke" or "Partial Nuke"... this is generally defined by the number of provisions the Nuke consists of. A "full" Nuke would be a level 30 farm full of troops/provisions (minus what's needed for buildings, generally 20 - 21k provisions worth of troops).
What is a Nuke? That can be anything. When it comes to troop builds there is only 1 truth in my experience on TW... don't mix O and D troops in a single village. Beyond that, everyone has their own preference and just about anything can work.
Nukes- This is a term used for Offensive troops. There are many thoughts on the number of troops and of what kind in a single Nuke (troops matched to attack ) This is something to look to your tribe and ask them the preferences and how each works. There are Nukes for different defenses and for different situations.
Sniping- The ability to send out your defense and pull it back at exactly the right point in order to take out a noble.
If anyone else sees these definitions different please jump in and add to this.
Doesn't need to be defense nor does it need to be pulled back.
Sniping is any activity that is intended to dodge the clearing wave or waves and intercept and kill the Nobles which generally have smaller escorts.
If a clearing wave lands at 02:36:01 and 2 nobles land at 02:36:02 and 2 more land at 02:36:03... sniping would be getting troops into the village at 02:36:03 to avoid the clearing wave, avoid the troops with the first Noble, and kill the troops and last 2 Nobles. Loyalty would be lowered in the village but 2 Nobles will never take a village from 100 loyalty to -1 so you'd buy yourself time to reinforce.