Use Female USB Type A as Power Supply for external device I bought a female USB Type A Breakout, like this (https://www.sparkfun.com/products/12700). I thought I could use this one to simply power a USB 5v water pump. Therefore I use an external USB power supply that is regulated by a relay, that I regulate with my Arduino. But I'm wondering if it is possible to get that USB Breakout to "give out" power to my water pump.
Yes. Just connect VCC to +5V and GND to GND and you can plug a 5V device into it.

If you need to use it as a charge port (for charging a phone) you will need to connect the D+ and D- pins together.