Happening upon refers to finding something unexpectedly, stumbling upon it by chance. Its antonyms, on the other hand, are related to the absence of chance and the intentional search for something. Words such as planned, scheduled, and arranged all suggest that the act of discovery was premeditated, prepared, and foreseen. Antonyms for happening upon could also convey a sense of intentionality, direction, and purpose. These could include seeking, looking for, or searching for. In contrast, some antonyms might imply a lack of interest or exposure, such as avoiding, shunning, disdaining, or ignoring.