deeply absorbed in thought; "as distant and bemused as a professor listening to the prattling of his freshman class"; "lost in thought"; "a preoccupied frown"

At the generic level, a name predated by use of the same generic or subgeneric name for another taxon at an earlier date. At the species level, a binomen for another species or subspecies used for another taxon at an earlier date.

having or showing excessive or compulsive concern with something; "became more and more haunted by the stupid riddle"; "was absolutely obsessed with the girl"; "got no help from his wife who was preoccupied with the children"; "he was taken up in worry for the old woman"

Already used and therefore unavailable for further use. Used of taxonomic names.