A Window-Licker is a reference to a retard whom only posseses the ability to twist his/her head and lick uncontrollably. Then crossed with the hilarious image of one licking a window.
Can be used in a one phrase sentence I.E 'Lickie-Window!'
Harry trys to ink bomb a person 2 rows infront in school. He proceeds to launch it, missing, hitting ginger haired, cadet crazed form teacher.
Aaron: (retard sounds) Lickie-Window Harry!
Tom: Lawrence is such a Window-Licker! Look at him play cricket!