opa

noun1

1. •
   Grandfather, grandpa.

   • We love to eat: Opa's apple cake […] My opa (grandfather) had a long and beautifully kept allotment in the north German town of Flensburg. — 2012

noun2

1. •
   Abbreviation of optionally piloted aircraft.
2. •
   Initialism of offensive patent aggregation.