So as we heat seekin' the seen heater sea-seein'

from Lupe Fiasco – SLR 3 (Round of Applause) Lyrics on Rap Genius

Meaning

Lupe is saying that we, the heat seekers (Lupe and other real rappers), are trying to take out the seen heater (fake rappers).
The fake rappers are sea-seein, could possibly be a triple entendre:
1. the fake rappers are sea-seein, they are lost in the ocean of Lupe’s tears.
2. the fake rappers are CC'ing(carbon copying), they are trying to make a carbon copy of Lupe’s music, they are trying to be like him.
3. the fake rappers are CC'ing(closed captioning), he can see that they are rapping, but can’t hear them because he is on another level, sort of the reverse of the dog whistle line he mentions in the next verse.

He could also be referencing the nursery rhyme “A Sailor Went to Sea"
"A Sailor went to sea sea sea
To see what he could see see see
But all that he could see see see
Was the bottom of the deep blue sea sea sea"
fake rappers try to understand his lyrics but keep getting lost

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