Thaumásios (θαυμάσιος) means wonderful, marvelous, astonishing — that which causes wonder and amazement. Derived from thaumazō (to marvel), it describes what transcends ordinary experience.
In Matthew 21:15, the chief priests are indignant at the 'wonderful things' Jesus did in the temple — healings and children's praise. The irony is sharp: those who should recognize the Messiah's wonders are offended by them. This contrasts with Psalm 118:23: 'The Lord has done this, and it is marvelous in our eyes.' God's works should leave us breathless with childlike wonder, not stiff with religious cynicism. All of God's redemptive acts — creation, exodus, incarnation, resurrection — are thaumásia.