What does "dirt" mean?

Additional senses

1. 2.In placer mining, earth, gravel, etc., before washing. Dirt bed (Geom.), a layer of clayey earth forming a stratum in a geological formation. Dirt beds are common among the coal measures. -- Dirt eating. (a) The use of certain kinds of clay for food, existing among some tribes of Indians; geophagism. Humboldt. (b) (Med.) Same as Chthonophagia. -- Dirt pie, clay or mud molded by children in imitation of pastry. Otway (1684). -- To eat dirt, to submit in a meanly humble manner to insults; to eat humble pie.
2. 3.To make foul of filthy; to dirty. Swift.