cat·ion·ic \|kad.ˌī|änik, -aˌtī-, -ēk\adjective 1.: relating to or consisting of cations 2.of a chemical compound: characterized by an active cation, especially by a surface-active cation (as a large hydrophobic organic group) < cationic germicide > < cationic surface-active agent > • cat·ion·i·cal·ly\-ə̇k(ə)lē, -ēk-, -li\adverb