- Not marked with or showing a date: an undated letter; an undated portrait.
- Being such as to have long-lasting appeal without ever going out of style: a classic, undated dress.
(comparative more undated, superlative most undated)
- (botany) Rising and falling in waves toward the margin, as a leaf; waved.
Latin undatus, past participle of undare (“to rise in waves, to wave, to undulate”).