act (up)on(redirected from acts upon)
1. To take action in a situation. The report is due tomorrow, so I need you to act on it immediately. Please act upon this subpoena for records at once.
2. To take action that is strongly influenced by certain information or advice. ("Upon" is most commonly used to convey this meaning.) Acting upon my doctor's orders, I cleared my schedule and spent the week recuperating at home. A; "I can't believe he said that about us!" B: "Well, he's probably just acting on his mother's instruction, and that woman hates us."
3. To impact in some way. The barking dogs next door are acting on my patience.
See also: act