Hilito is the diminutive form of hilo (thread), so it literally means "little thread". The -ito ending is a common way in Spanish to make something sound smaller or to add a sense of affection.
In the song, Romeo Santos uses this word as a powerful metaphor for vulnerability. He sings, "Colgando en un hilito sin tu amor" (Hanging by a little thread without your love), creating a vivid image of being in a fragile and precarious state after losing someone's love. It's the central theme and title of the song, making it a perfect word to learn.
Romeo Santos takes a massive hit to his pride in "Hilito", and he is completely honest about how badly he messed up. He used to think of himself as an unbeatable player in romance—bragging with the Dominican slang privaba en vencedor ("pretended to be a winner")—only to end up in total checkmate (jaque mate). Now, he compares his reckless arrogance to an acrobat doing dangerous stunts on a fragile little thread: Me confié de trapecista en un hilito / Y resbalé por la arrogancia yo lo admito ("I trusted myself like a trapeze artist on a little thread / And I slipped because of arrogance, I admit it"). When he tries to command his own heart and soul to move on, they literally scream back and laugh in his face.
The drama gets even better with his over-the-top cultural shoutouts. He calls his breakup a Crónica de una muerte anunciada ("Chronicle of a Death Foretold," referencing the famous Gabriel García Márquez novella title), stares at a colorless Mona Lisa portrait left behind in his bedroom, and admits that his tough-guy act completely failed: No valoré tu amor y me sentí Tarzán / Y todos los hombres lloran hasta Superman ("I didn't value your love and I felt like Tarzan / And all men cry, even Superman"). Asking him to forget this romance is as impossible as demanding the moon and the sun rise together, leaving him hanging by a literal thread without her.