Definition of redtop:
(n) :
(uncountable) A kind of grass (Agrostis vulgaris) highly valued in the United States for pasturage and hay for cattle.
(n) :
(countable) Species of the genus Agrostis, the bentgrasses.
(n) :
Alternative form of red top (“tabloid newspaper”). [(UK, Ireland, journalism) A tabloid newspaper, particularly one of those considered to have lower journalistic standards than the broadsheets.]