Hydrophobe (Greek, "water-fearing) is a property of a molecule and means it is repelled by water. Hydrophobic molecules tend to cluster together. H2O molecules can build hydrogen bonds to stabilize each other, which explains the unusual chemical properties of water. In water, these hydrogen bonds are constantly shifting. A hydrophobic molecule cannot establish hydrogen bonds with water, thus limiting the "freedom" of H2O for switching hydrogen bonds, which makes the whole area around the hydrophobic molecule energetically adverse. As one larger area of this kind is energetically more favourable than two smaller ones, thermodynamics favour hydrophobic molecules clustering together, even though hydrophobic molecules are not actually attracted to another.
Note also: Hydrophobia also means "rabies" in English.