Loucura translates to "madness" or "craziness". It's a strong and evocative word that immediately grabs attention.
In "Estranha Loucura", the singer uses it to describe the strange, almost irrational, nature of his love and devotion. He's aware of the 'madness' in his actions – constantly forgiving, taking blame, and depending on someone who hurts him – yet he can't stop. This word perfectly encapsulates the intense, self-sacrificing, and somewhat self-destructive love depicted in the song.
"Estranha Loucura" ("Strange Madness") is Alexandre Pires singing about a love he can't explain, even to himself. He calls it madness because it makes no sense: trying to understand someone who won't be understood, forgiving what shouldn't be forgiven, taking the blame every time a fight ends just to get back into her arms.
He knows the relationship is one-sided. He gives in completely, plays the guilty one even when he isn't, and lets himself be humiliated, all because he's dependent on her. He admits he has already paid a heavy price for loving her too much, while she treats it all as if it barely matters.
The chorus turns the tables. He warns that when he finally leaves, she'll be the one left missing him, trying to hide it while her heart aches. It's a song about giving too much in love, and about believing that walking away will finally make the other person feel what he felt.