A.T. Robertson Commentary Mark 16:11

"And they, when they heard that he was alive, and had been seen of her, disbelieved." — Mark 16:11 (ASV)

Disbelieved (ηπιστησαν). This verb is common in the ancient Greek, but rare in the N.T. and here again verse 16 and nowhere else in Mark. The usual N.T. word is απειθεω. Luke 24:11 uses this verb (ηπιστουν) of the disbelief of the report of Mary Magdalene and the other women. The verb εθεαθη (from θεαωμα) occurs only here and in verse 14 in Mark.