One or the other of two (6)
I believe the answer is:
either
(Other definitions for either that I've seen before include "Each of two; moreover" , "One of two alternatives" , "offered a choice" , "could be one of two" , "Her tie (anag.)" .)
I believe the answer is:
either
(Other definitions for either that I've seen before include "Each of two; moreover" , "One of two alternatives" , "offered a choice" , "could be one of two" , "Her tie (anag.)" .)