Guango is an informal Spanish word for loose. I hadn’t heard it before coming to Mexico, but it’s common enough here. I associate it with overly loose clothing: Te queda guango. That looks (too) big on you. For example, overly baggy pants. It also has a derogatory sexual meaning: una panocha guanga is a loose, fucked-out pussy.
The more neutral word for loose is flojo. The dental assistant said flojito to get me to relax my jaw. Flojito y cooperando means without putting up resistance, especially in the context of sex. Hoy te quiero flojita and cooperando. Today I want you to be in a yes mood.
Flojo, as you know, is also the usual word for lazy, a less formal alternative to perezoso. No seas flojo. Don’t be so lazy. Flojera, like its dirtier cousin, hueva, is the feeling of laziness. ¿Tienes flojerita? Do you feel lazy right now, without energy? Me da flojera is an informal but clean version of me da hueva, a way to say that something bores you to tears or doesn’t interest you in the least. ¡Qué flojera! That’s pathetic.
Aflojar is the action of making something flojo, for example, loosening a screw. Aflojar (una lana) means to not be stingy with money. In a sexual context, aflojar means to put out, give it up, let someone have sex with you. For example, Esa vieja no va a aflojar contigo. She’s not going to have sex with you. With an indirect object: No le quiere aflojar a Ramiro. She doesn’t want to put out for Ramiro.