worsen

To make worse; to impair.

Near-synonyms: aggravate, exacerbate; degrade, deteriorate; see also Thesaurus:aggravate

Global warming has worsened the weather.

To become worse; to get worse.

The weather has worsened.

During the day conditions worsened quickly—for example, a 2-6-0 on the Uckfield line suddenly encountered flood water high enough to enter its ashpan and extinguish its fire—until lock gates up-river at Barcombe gave way and a tidal wave rolled down the valley meeting head-on a spring tide rolling up from the coast.

To get the better of; to worst.