nonplus (v.)

"to bring to a nonplus, to perplex, puzzle, confound," 1590s, from the noun nonplus "state in which one is unable to proceed or decide" (1580s), usually in a phrase such as at or to a nonplus, properly "state where 'nothing more' can be done or said," from Latin non plus "no more, no further" (see plus). Related: Nonplussed.