atalayar

A somewhat literary verb meaning to keep watch over a field, coastline, or territory from a high point (an atalaya, or watchtower) to spot anything approaching — and by extension, to spy on or closely observe someone's actions. It survives mostly in historical, military, or literary writing rather than everyday speech, where vigilar or observar is far more common.

• Los centinelas atalayaban la costa desde la torre. — The sentries kept watch over the coast from the tower.
• Atalayaba los movimientos del enemigo desde la colina. — He watched the enemy's movements from the hill.
• Sentía que alguien atalayaba cada uno de sus pasos. — He felt like someone was watching his every move.

Reaching for atalayar in casual modern speech — it reads as historical or literary, so vigilar or observar is the natural everyday choice for "to watch/keep an eye on."

Often confused with vigilar.