If something is oblique, it has a slanting position or direction. In figurative use, oblique means indirect or purposely misleading. "What is two plus two?" "Fish!" as an answer is completely oblique.
In math, this adjective refers to geometric lines or planes that are not parallel or perpendicular to a line or surface. A playground is positioned at an oblique angle to the ground. By correcting the clerk's "Mrs." with "That's Ms. now," the woman made an oblique reference to her change in marital status.