As related to BL comics.

Somewhat a joke. Somewhat not. Please correct me if I'm wrong on a definition.

Alpha by western alphabet. Done in katakana, but sounds are done in hiragana too.

'Biku/Bikun' is the reaction to being (very) startled. 'Biku' can be shaking and trembling, and 'bikun' can also indicate an orgasm.

'Doki' indicates a heartbeat, possibly a shocked reaction to something as well ("eh?!" heartbeat).

'Dokun' is like 'doki', but is a hard heartbeat. You can get 'doki doki', but I've never seen 'dokun dokun', possibly because to get the emphasis, only one hard heartbeat is needed. It indicates (extreme) shock, or can be used to indicate orgasm.

'Dosa' is a soft whump, flump. Think, landing on a pillow or tossing something soft onto the floor. If it was a hard hit, it would be 'don' or 'ban'.

'Guchi'. Heh. I like to think of this as a squelching sound. ...

'Gyu' is for squeezing. Can be a hug, can be squeezing something smaller, can be clenching a fist... etc.

'Hiku/Hikun' is a hiccup, where 'hikun' is a really big hiccup. Or, they could mean the person is startled. Multiple 'hiku' can be crying, or trembling.

'Hyoi' indicates heavy lifting, or at least the lifting of something large.

'Niya/niyari' is an evil smile, a smirk. If 'niko' is for a normal, guileless smile, 'niyari' is a smile that has intentions behind it.

'O to to' Sometimes, a person lifting something heavy will say this. It's a bit like saying, "oomph."

'Pero' is a licking sound.

'Su/suru' is a slippery sound, like cloth sliding over hands or a sliding step (just 'su'). It's a smooth movement.

'Zu' is often a move with force behind it, a violent motion. Repeated 'zu zu zu' is a series of them, and it appears that 'zu' before anything means that the movement is forceful. I've also seen it used to show sliding down a wall.

'Zuru' is for sliding, like sliding down a wall.