from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Two and a half times as large; having the ratio of 2.5 to 1.
from the GNU version of the Collaborative International Dictionary of English
- adj. Twice and a half as great (as another thing); having the ratio of two and a half to one.
from The Century Dictionary and Cyclopedia
- Being in the ratio of 2½ to 1, or 5 to 2.
sesqui- + duplicate (Wiktionary)