"Special K" or ketamine like substance drug. More specifically horse traqulizer. Statement is easily perceived as a "girthy hung penis", thus those around to hear the statement believe homosexualintercorse which they won't object to due to the current social acceptance climate.
Something optimus presumably isn't carrying. It's also the name of one of optimus songs. Horser is slang for many things like drugs guns etc. It's commonly heard at gas station in the morning by local crackheads. The slang may also refer to the sepcefic drug ketamaine.
A horser is a what ever you want it to be becuase no one knows what a fucking horser is. like what the fuck is a horser like is it a gun or does it mean you got that meat idk
The crackhead at the gas station leans in to ask you: yo you got that horser on you