Thayer's Greek Lexicon

 1. what is wiped off
2. dirt rubbed off
3. off scouring, scrapings

The Athenians, in order to avert public calamities, yearly threw a
criminal into the sea as an offering to Poseidon; hence the term
became used for an expiatory offering, a ransom, for our child, i.e.
in comparison with the saving of our son's life let it be to us a
despicable and worthless thing. It is used of a man who in behalf of
religion undergoes dire trials for the salvation of others.