The winger has signed his dual registration with the Hornets and will be available for them in their Emirates FA Cup Third Qualifying Round match at home to Hanworth Villa on the weekend.
As part of the deal with the Isthmian Premier Division outfit, Meekums has been cleared to play in all cup competitions for the Hornets this season.
The initial plan for the deal will see Meekums move to Horsham for the next month, with the position to be reassessed after that point.
The 24-year-old has made 202 career appearances for the Rebels, scoring 40 goals in all competitions.
Meekums has found first-team minutes hard to come by of late, making just two starts in all competitions for the Reds.
Adam Hinshelwood commented on the move, “It’s quite a simple one for us, this. Meeks needs some game time and Horsham can offer this to him for a month.
They are getting a great player and person and then we will assess it after that and see where we are. They can see how he is doing from their side and then make plans from there”.