A person with little interest in anything other than themselves and who possess no capacity to drive in only one lane at a time. The fuckwit may be observed in all walks of life. When unsure of an individual's status, proceed with caution, and try to think "Look out, there's a fuckwit about."
Fuckwits cannot see you, so always keep them in front of you. Fuckwits have no capacity for thought or observation, either driving a car or walking in a shopping mall.