The windshield is menstrual/minstrel
The most likely interpretation, given the context, is that Lupe is mispronouncing the word “menstrual” to fit in with the next bar; his windshield is so covered in chicken and/or deer blood that it looks like… well, you know
He may also be saying “minstrel”: his windows are tinted, like the black face of a performer at minstrel shows (popular in the antebellum and post-Civil War South, involving whites dressing up as black caricatures). On a deeper level, Lupe may also be suggesting that when he surveys the rap scene he sees a minstrel show — a cacophony of buffoonish stereotypes.
Minstrel here might also refer to The Minstrel Show, an album by Little Brother. BET refused to play one song, “Lovin' It”, because they deemed it “too intelligent”.
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