Definitions
1.noun(obsolete outside dialectal) An ant.
2.nounAn insignificant person.
3.nounA person who adheres strictly to a rule or policy despite current circumstances."Their manager is a real pissant about break times."
4.nounA person seemingly incapable of focusing on anything but the trivial, especially in the sense of trivial or irrelevant criticism.
5.adjectiveInsignificant or unimportant.