【Urge】 , 【egg】 ,  【exhort】 ,  【goad】 ,  【spur】 ,  【prod】 ,  【prick】 ,  【sic】  mean to press or impel to action, effort, or speed.

【Urge】 implies the exertion of influence or pressure either from something or someone external or from something within (as the conscience or the heart); specifically it suggests an inciting or stimulating to or toward a definite end (as greater speed or a prescribed course or objective) often against the inclinations or habits of the one urged.

【Egg】 usually presupposes a hesitant, inert, or lagging will and usually suggests an encouraging or even an abetting.

【Exhort】 may suggest the arts of a preacher or orator inciting men to good or better lives or actions and usually implies a fervor or zeal characteristic of a preacher in stimulating through admonition, encouragement, or pleading.

【Goad】 basically denotes the use of a pointed rod in driving cattle and carries in its extended use a strong implication of something that irritates or inflames and drives one on in spite of inclinations or habit of yielding to other desires or motives.

【Spur】 basically applies to a spiked device attached to the heels of a rider and used to 【urge】 on a lagging horse; it is likely to suggest in its extended use a superior impulsion that makes up for the weakness or reluctance of one's nature or will.

【Prod】 implies a being driven or forced into action as if by means of a stick or 【goad】 and may suggest a thrust or a push and an impelling against one's will.

【Prick】  comes close to  【spur】 in implying an impulsion from something sharp-pointed or irritating that serves to 【urge】 or drive.

【Sic】 basically means to 【urge】 on a dog to chase or attack someone; with persons it often implies exhorting or goading to attack or worry.