adj. 1. Not legally or factually valid; null: an invalid license. 2. Falsely based or reasoned; faulty: an invalid argument. [Latin invalidus, weak : in-, not; see IN-1 + validus, strong (from valēre, to be strong; see wal- in the Appendix of Indo-European roots).] in′va·lidi·ty (-və-lĭdĭ-tē) n. in·valid·ly adv. |
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