<p><strong>Adjective:</strong></p><ul><li>deviating from the usual or proper course in conduct or opinion; eccentric: erratic behavior.</li><li>Synonyms: capricious, unstable, unpredictable.</li><li>Antonyms: stable, regular, consistent.</li><li>inconsistent, irregular, or unpredictable: Many factors affect purchasing power, such as inflation and erratic swings in the stock market.</li><li>having no certain or definite course or pattern; wandering; not fixed: erratic winds.</li><li>Geology: noting or pertaining to a boulder or the like carried by glacial ice and deposited some distance from its place of origin.</li><li>(of a lichen) having no attachment to the surface on which it grows.</li></ul><p><strong>Noun:</strong></p><ul><li>an erratic or eccentric person.</li><li>Geology: an erratic boulder or the like.</li></ul>