Of an action, occupation, etc.: requiring earnest thought; demanding or characterized by careful consideration or application; performed with…

Of intellectual operations, thought, etc.: Conforming to an exacting standard of mental effort; rigidly exact or accurate; grave, serious, not…

Weighing upon the mind or feelings. Obsolete.

Requiring or involving considerable mental exertion.

Marked by, or involving, serious study or intention; not light, frivolous, or merely amusing.