What is the definition of a one-shot item?
 

Is it a declaration that the item can only be used once, or is it any item that is discarded after use?

Re: What is the definition of a one-shot item?
 

It is an Item that can only be used once. They will almost always have "Usable once only" text included on them. Some cards, like Wand of Dowsing, which is clearly a use once and discard type card are also given a bit of leeway to call them a one-shot Item too, as per the following info from the FAQ:

Items that give you something while on the table, but allow you to discard them to do something else, such as Rat on a Stick are never considered one-shot Items. They cannot be played for their discard ability from your hand.

I think that covers most cards, but if you are still confused over any particular cards, please indicate which.

Re: What is the definition of a one-shot item?
 

Specifically, I'm asking about cards like Time Warp or Tchoo Tchoo People.

Time Warp cancels a one-shot card. Would that include a wandering monster card?

Tchoo Tchoo People requires you to play all one-shot cards in your hand. Would that apply to cards that don't specifically say "usable once only" or "discard after use"?

Re: What is the definition of a one-shot item?
 

Both of those cards seem pretty specific. Tchoo Tchoo people refers to cards that would help you in combat and time warp can cancel anything that can only be used once.

Re: What is the definition of a one-shot item?
 

Time Warp can cancel only Traps and one-shot ITEMS, not "anything that can only be used once."

Re: What is the definition of a one-shot item?
 

Moldon is, of course, correct in that Time Warp specifies one shot Items.