Sazekiel

When Sam is attacked by demons in 9.02 Devil May Care Ezekiel takes over

Sazekiel refers to the angel Ezekiel when he is possessing Sam. It is a portmanteau made up of the two character names.

It arose in fandom after 9.01 I Think I'm Gonna Like It Here when in order to save Sam who is dying after undertaking the Trials, Dean helps the angel Ezekiel possess Sam, ostensibly in order to heal him. Sam is unaware of this, however Ezekiel can at times take over Sam, act through him and converse with Dean.

A similar mashup form - Samifer - was used when Lucifer possessed Sam in 5.04 The End.