SCIENCE!
Ship-sinking monster waves revealed by ESA satellites / Observing the Earth / Our Activities / ESA
http://www.soest.hawaii.edu/PubServi.../Rosenthal.pdf
Oh yes, they are out there, and a lot more than previously thought.
My layman's explanation is...... remember as a kid you were in the bathtub making waves..... and suddenly something larger happened and it splahed all over the bathroom floor and your mother got all mad? That's a rogue wave.