The phrase "cropt up again" implies the sudden or unexpected appearance of something. Its antonyms, therefore, would include words that suggest predictability, consistency, and stability. Words such as "steady," "consistent," "regular," and "expected" all convey the opposite of "cropt up again." Other antonyms might include phrases like "continuously present," "always around," or "never absent." Essentially, any words that suggest a lack of surprise or unpredictability would be fitting antonyms for "cropt up again." By understanding these antonyms, we can better grasp the full range of meanings and implications that come with the phrase.