As an adjective optional
is not compulsory; left to personal choice; elective.
As a verb instigate is
to goad or urge forward; to set on; to provoke; to incite.
Not compulsory; left to personal choice; elective.
- On that beach clothing is entirely optional .
To goad or urge forward; to set on; to provoke; to incite.
- He hath only instigated his blackest agents to the very extent of their malignity. -Bp. Warburton.
Commonly used with reference to evil actions; as, to instigate one to a crime.
* (to goad or urge forward): animate, encourage, impel, incite, provoke, spur, stimulate, tempt, urge
* (to goad or urge forward): halt, prevent, stop