Petroleum based pomade used to style the hair. Favoured less in recent times due to all manner of modern waxes, hairsprays amd gels but still de rigeur amongst the swing, rockabilly, and greaser fraternities.
Can be used to create anything from a slicked back 1920s look to a 1950's pompadour.
Have you got any grease? I'm going Lindy Hopping tonight and I want my pomp to look right.