When one is pretending one has a partner (normally fantasisical), in the bed with them and talks to the pillow. It is also used to describe when two people chat pointlessly before/after sex.
A: That was great weren't it?
B: Yeah, so what you doing tomorrow?
A: Dunno, you?
The bummy bummy stimulation one gets from mounting the linen of life.
Pillowtalk originated from the pointless conversation couples had before/after sex. This has since elvolved to the slimulation vocal noise that erupts from ones mouth whilst enjoying a mounting session with the pillow itsself.
Person A: Alex makes love to his pillows
Person B: Mmmmmmmmmmmm Pillowtalk