Morno translates to "lukewarm" or "tepid." It's an interesting word because it describes a state of being neither hot nor cold, which is central to the song's theme.
In "Choque Térmico," the singer uses morno to express that their relationship can't exist in an in-between state. He declares, "não tem morno," meaning there's no room for lukewarm feelings; it's either all or nothing, hot or cold. This word perfectly encapsulates the emotional push and pull of the song.
Tierry's "Choque Térmico" is all about that push-and-pull, on-again-off-again relationship that's driving him crazy! He sings about how his partner's "coração frio e o beijo quente" [cold heart and hot kiss] are causing a "choque térmico na gente" [thermal shock in us]. It's a constant cycle of "esquenta, esfria" [heats up, cools down], making their whole vibe unstable. He even worries, "Já já eu fico doente" [Soon I'll get sick] from all the drama!
He's tired of the hot and cold, the constant fighting when one just wants to chill, and feeling like he's always present while she's absent. Tierry makes it clear: if they're going to try again, there's no middle ground. "Não tem morno / Ou a gente congela ou pega fogo" [There's no lukewarm / Either we freeze or we catch fire]. He'd rather have the "calor da Bahia" [heat of Bahia] than the "gelo da Europa" [ice of Europe], showing he's ready for passion, not a chilly distance. It's a fun, relatable take on a love that just can't find its balance!