abismar

Literally to plunge something into an abyss, but far more commonly used reflexively — abismarse en algo means to become deeply absorbed or lost in thought, contemplation, or grief, sinking into it as if into a chasm.

• Se abismó en sus pensamientos durante el viaje. — He became lost in thought during the trip.
• La noticia lo abismó en una tristeza profunda. — The news plunged him into deep sadness.
• Prefiero no abismarme en dudas antes de decidir. — I'd rather not sink into doubt before deciding.

Learners sometimes treat abismarse as a simple synonym of concentrarse (to concentrate) — it carries a heavier, more emotionally weighted sense of being swallowed up by thought or feeling, not neutral focus.

Often confused with sumergirse.