Strong’s Greek
G5326 — phantasma
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
φάντασμα
phantasma — pronounced fan'-tas-mah
from 5324; (properly concrete) a (mere) show ("phantasm"), i.e. spectre:--spirit. see GREEK for 5324
2 occurrences in the KJV.
Matthew 14:26
And when the disciples saw him walking on the sea, they were troubled, saying, It is a spirit; and they cried out for fear.
Mark 6:49
But when they saw him walking upon the sea, they supposed it had been a spirit, and cried out: