What component does this MOSFET-like symbol represent?
A MOSFET (p-channel).

The central pin is the Substrate or Bulk, the outwards arrow means that it's a p-MOS.



The image (found on Wiki) shows how the MOSFET is internally; the Bulk contact is connected to the substrate where the transistor is build upon. If not tied to the source, the Body effect changes the threshold voltage, altering the current output.

Usually Bulk and Source are connected together, like in the case of discrete MOSFETs; however, in integrated circuits design, like VLSI (very large scale integration), entire rows of transistors (all p or n channel) share the same substrate, and thus have it connected to Vdd.