Alighting upon is a phrase that means to come across or discover something by chance or accident. However, there are several antonyms for this phrase, including avoiding, evading, missing, overlooking, and neglecting. Avoiding means to intentionally stay away from something, while evading means to escape or avoid something by using deception or cunning. Missing refers to failing to find something that was expected or desired, while overlooking means to fail to notice something that is right in front of you. Neglecting means to ignore or pay little attention to something, which can result in missing out on valuable opportunities.