1.adjectiveCausing vexation or annoyance; teasing; troublesome.
2.adjectiveFull of trouble or disquiet
3.adjective(of an action) Commenced for the purpose of giving trouble, without due cause.
"a vexatious lawsuit"
4.adjective(of a party or entity) In the habit of starting vexatious litigation and therefore liable to have restraints placed on one's ability to access the courts.