bitter principle(n = noun.substance) - any one of several hundred compounds having a bitter taste; not admitting of chemical classification;
is a kind of chemical compound, compound

accounting principle, archimedes' principle, basic principle, bitter, bitter almond, bitter almond oil, bitter aloes, bitter betch, bitter cassava, bitter chocolate, bitter cress, bitter dock, bitter end, bitter floom, bitter hickory, bitter lemon, bitter orange, bitter orange tree, bitter pea, bitter pecan, bitter pignut, bitter pill, bitter salts, bitter spar, exclusion principle, first principle, fundamental principle, gestalt principle of organization, guiding principle, huygens' principle of superposition, in principle, indeterminacy principle, judicial principle, le chatelier principle, le chatelier's principle, le chatelier-braun principle, legal principle, life principle, localisation principle, localization principle, mass-action principle, moral principle, pauli exclusion principle, pleasure principle, pleasure-pain principle, pleasure-unpleasure principle, principle, principle of equivalence, principle of liquid displacement, principle of parsimony, principle of relativity, principle of superposition, reality principle, superposition principle, uncertainty principle, vital principle, working principle