the time when an hour begins on the clock.

We'll update the weather again at the top of the hour.

Related vocabulary: the bottom of the hour

• be the making of
• be the making of someone
• be the marrying kind
• be the meat in the sandwich
• be the model of
• be the model of something
• be the nature of the beast
• be the only pebble on the beach
• be the order of the day
• be the picture of
• be the picture of health
• be the picture of [health/innocence etc.]
• be the picture of innocence
• be the right side of
• be the salt of the earth
• be the soul of discretion
• be the spitting image of
• be the spitting image of someone
• be the talk of the town
• be the toast of
• be the toast of someone
• be the worse for wear
• be the wrong side of
• be thick on the ground
• be thinner than all get out