Is it permissible to rub against a pillow and imagine intercourse to relieve psychological pressure, knowing that this does not lead to the emission of semen (mani) or pre-seminal fluid (madhy)?

Rubbing against a pillow or other objects in pursuit of pleasure is impermissible, just like all other forms of masturbation, regardless of the means. Ibn 'Uthaymeen explained this by stating that the underlying reason (for prohibition) is the same, and the emission of maniy (semen) or madhiy (pre-seminal fluid) is not a prerequisite for this rubbing to be forbidden.