(adj) exceedingly or unbelievably great, Example:the bomb did fantastic damage; Samson is supposed to have had fantastic strength; phenomenaRl feats of memory
a. [ Cf. F. phénoménal. ] Relating to, or of the nature of, a phenomenon; hence, extraordinary; wonderful; as, a phenomenal memory. -- Phe*nom"e*nal*ly, adv. [1913 Webster]