"A-ok" is a term used to denote that everything is going well or is satisfactory. Some of the antonyms for this term could be "unsatisfactory", "inadequate", "inefficient", "disappointing", "underwhelming", "substandard", "deficient", "faulty", "unacceptable", "imperfect", "subpar", "incompetent", "flawed", "inferior", and "unsound." These antonyms describe situations where things are not going as planned or are not up to standard. It is important to note that these antonyms are context-dependent, and the meaning of the term "a-ok" and its antonyms can differ based on the situation or the subject matter.