acodarse

To lean on one's elbows — resting on a table, railing, or windowsill: acodarse en la barra, acodarse en la ventana. Almost always used reflexively.

• Se acodó en la barra mientras esperaba su pedido. — He leaned on his elbows at the bar while waiting for his order.
• Nos acodamos en la baranda para ver el paisaje. — We leaned on the railing with our elbows to look at the view.
• Le gusta acodarse en el balcón por las tardes. — She likes to lean on her elbows on the balcony in the evenings.

It specifically means leaning on the elbows, not just leaning in general — for leaning your back or body against something, apoyarse is the broader verb.