Baptismos (βαπτισμός) refers to ritual washing or ceremonial cleansing, distinct from baptisma (G908) which typically refers to John's baptism or Christian baptism. Baptismos appears in Mark 7:4, 8 (Jewish ceremonial washings), Hebrews 6:2 ("instruction about baptisms"), and Hebrews 9:10 (OT ceremonial regulations involving washings).
Baptismos in Hebrews 9:10 refers to OT ceremonial washings — external regulations that could not cleanse the conscience (Hebrews 9:14). These were shadows pointing to the cleansing that only the blood of Christ can accomplish. Hebrews 6:2 includes "instruction about baptisms" among foundational Christian teachings, suggesting the early church carefully explained the difference between Jewish purification rites, John's baptism, and Christian baptism. The OT washings (baptismoi) were types; the antitype is Christ's blood and the Spirit's regenerating work.