Most of these are just implementation details, so they don't necessarily "mean" anything in a larger sense. If you want to ask people who know the details, ask your question over on forums.swift.org.
Here's what I know about a couple of them:
A protocol witness table is a descriptor of where to find the implementation details of a type's conformance to a protocol. (The position within the table is specific to the protocol, the information at that position is specific to the type.)
A function signature specialization is a version of a generic function signature that as a specific type, as opposed to the generic type.
"Owned to guaranteed" sounds like ARC ownership information, perhaps allowing some unnecessary retains and releases to be eliminated.
Partial application is a way of applying some parameters to a function (or closure), but not all of them, producing a slightly different closure with fewer parameters.
Reabstraction is probably a technique for modifying a calling convention from one "abstraction" (calling convention, data representation, etc) to another, for example when calling C or Objc-C functions, or passing native Swift data structures. A thunk is, of course, a tiny piece of code that allows one kind of code to transfer to a different kind of code.
