from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A calling to witness.
- n. The vehement expression of desire put in terms of "for someone's sake" or "for God's sake."
from the GNU version of the Collaborative International Dictionary of English
- n. An invocation of, or address to, the Supreme Being.
This was related to Father Albuquerque,  who after a fervent deesis entreating compassion on the natives, went to the island, exorcised the evil spirits there and blessed the land.
The more common opinion is that the distinction is twofold; first, that proseuche is addressed only to God, whereas deesis may be addressed to men; and secondly, that the former includes all address to God, while the latter is limited to petition.
As to the difference between proseuche and deesis, prayer and supplication, some say that the former has for its object the attaining of good; the latter, the avoidance of evil or deliverance from it.