Works on prayer seldom mention this word, which occurs 60 times in the AV. It is a form of intensified prayer by which God’s help is fervently implored in a time of special need. It is to prayer what fire is to incense.
Supplication may be no more than a cry to God; the word is used in 1 Pet. 3:12, RV as a translation of the word cry in Psa. 34:15. The same word is used of the cry of the Jews during their Egyptian bondage, Ex. 3:7. Sometimes it is a wrestling with God like that of Jacob when he would not let the angel go until he blessed him, Gen. 32:24-29. The encounter was so intense that Jacob wept on that occasion, after which he was given power with men and with God, Hos. 12:3, 4.
The outstanding NT example is Christ in Gethsemane. His supplication was accompanied by “strong crying and tears,” Heb. 5:7. Our Lord’s mighty works were done with no sign of effort, but in this prayer He experienced travail and anguish of soul. Paul’s deep concern for the salvation of Israel resulted in supplication, Rom. 10:1, RV.
The word is found in Phil. 4:6 between prayer and thanksgiving.
An outstanding revelation about supplication appears in Jas. 5:16. A new disclosure informs us that Elijah prayed, 1 Ki. 18:42, where the OT is silent. Associated with this fact is the statement that supplication (RV) avails much.
William Evans, The Great Doctrines of the Bible, (Chicago: Bible Institute Colportage Assoc., 1912), WORDsearch CROSS e-book, 318.