The Suda glosses here the original compound kerasfo/ros (literally: horn-bearing), which preserves the nominative in its first component, with the more transparent keratofo/ros, using the late third declension.
The form presented here (though not in other lexica: see the references at Photius kappa590 Theodoridis) is the masculine accusative plural. It is attested four times before the Suda, and the likeliest source is Sophocles fr.89 Radt, quoted in Aelian, History of Animals 7.39: "[the deer] lifting its nose ... and the tines of its horns crept at ease".