A small horse-drawn cart.
"The old buggy creaked softly as it rolled down the dusty country lane toward the barn."
infested with bugs
"The old barn was so buggy that we couldn't even sit in the porch without being bitten by mosquitoes and fleas."
Infested with insects
"After leaving the fields open all summer, the old shed became a buggy haven for mosquitoes and flies."
The origin of the word buggy is unknown. Its earliest meaning referred to a light carriage with two wheels, but even that definition does not explain where the term came from.