spinlock, spinwait in c# -- phrasebook

Smart spin -- Both use smart spin. Traditionally, spin means hogging the driver's seat unproductively, so other threads won't get the time slices. Smart spin constructs don't hog the driver's seat for long.

lockfree -- both contribute to lockfree algorithms, but
** Spinlock is unrelated to CAS.
** Spinwait doesn't use CAS[1] but is often used with CAS

context switch -- minimized. Both constructs minimizes context switch. The spinning thread doesn't give up driver's seat but spins briefly and then (hopefully) enters critical section.

optimistic -- "brief" spin and retry

[1] according to my analysis. See MSDN
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Spinlock is comparable to a regular lock. A thread hitting a contended regular lock immediately, automatically gives up CPU (context switch). With a spinlock, the thread spins briefly if contended, then hopefully (optimist!) enters the critical section, without context switch. There are many differences but that's the big picture.