quintagenarian means One who is between the ages of 50 and 59, inclusive. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
noun
- One who is between the ages of 50 and 59, inclusive.“That would be bad enough, God knows! but what is it to finding yourself in an infernal "fix," at a dinner-table, with a literary quintagenarian at your elbow […]”