to gradually become worse.

The area has started to go downhill economically in the last ten years.

We started to argue soon after we got married, and things went downhill from there.

• hidden agenda
• hide a multitude of sins
• hide head in the sand
• hide light under a bushel
• hide your head in the sand
• hide your light under a bushel
• high and mighty
• highest rung on the ladder
• high-flier
• high ground
• high jinks
• highly-strung
• high roller
• highways and byways
• hinge on
• hinge on something
• history in the making
• hit a brick wall
• hit a home run
• hit and miss
• hit a nerve
• hit a raw nerve
• hit a snag
• hit a wall
• hit back