Desentendido

Like desconocer, the verb desentenderse is one of those -des words whose relation to its root is not immediately obvious. Since entender means understand, you might be scratching your head wondering what 'un-understand' could mean. It turns out that desentenderse means ignore or pretend not to know or notice something — an intentional forgetting, if you will. Since we humans lie and deceive, this is a handy word for many situations.

No te hagas el desentendido

• No me puedo desentender. I can't just pretend like I don't know. I'm morally obligated to respond.
• No te hagas el desentendido. Don't act like you don't know what I'm talking about! Literally, don't make yourself the one who doesn't understand. Naturally, if the accused is female, adjust accordingly: No te hagas la desentendida.
• ¡No te hagas!. This is basically a shorter version of No te hagas el desentendido. Don't play dumb.
• Se desentendió de nosotros. He abandoned us, our family. He refused to recognize us as his children.

As you can see, desentenderse captures the idea of willfully ignoring a situation to the point of pretending it doesn't exist at all.

Hacerse de la vista gorda

A related expression is hacerse de la vista gorda, look the other way, overlook. Literally, make your view of something fat.

• El poli se hizo de la vista gorda. The officer pretended not to notice what was going on. He looked the other way and did nothing, allowing the criminal activities to continue without interference.