(education, sometimes mildly derogatory) An educator, especially at the postsecondary level, who imparts knowledge by lecturing to an audience; the method of imparting knowledge used by such an educator.

(education) An educator whose method is to provide students with occasional advice, assistance, and correction while allowing them to explore a subject area independently or by interacting among themselves; this educational method itself.

(colloquial, of a person) Extremely busy.

(slang, derogatory, Canada, US, vulgar) To be oblivious to the real state of things, from either stupidity or stubbornness.

simple past tense and past participle of switch on

(informal) Highly attentive and mentally engaged.

Being right once doesn't prove anything.

(idiomatic, euphemistic) To defecate or urinate. / (dated) To ruin somebody.

(idiomatic) To feel compassionate, especially in order to forgive someone or to be willing to help them in some way.

(idiomatic) Having a period of enthusiasm towards some activity.