pro·pel·ler·head 
(prə-pĕlər-hĕd)
(prə-pĕlər-hĕd)n.
Slang
Slang
One who is highly skilled in a technical field, especially computer science, but who is often considered socially inept.
[From the small propeller on top of the beanie often worn by caricatures of scientifically knowledgeable persons in popular culture.]