PTO

Short definition from Wiktionary

Proper noun

1. 1
   Initialism of Patent and Trademark Office
2. 2
   Initialism of Patent and Trademark Office: United States Patent and Trademark Office.

Noun

1. 1
   Initialism of parent-teacher organization.
2. 2
   Initialism of paid time off.
3. 3
   Initialism of power take-off, a powered shaft for driving auxiliary equipment.
4. 4
   Initialism of pick-to-order.

Phrase

1. 1
   Initialism of please turn over (written at the end of the text on a page to say that it continues overleaf).