The spell that Seamus Finnigan uses to try and turn his goblet of water into rum. Much like everything else that he tries to put spells on, the water explodes in his face.
Seamus: Eye of rabbit, harp string hum, turn this water into rum!
Harry: Ron, what's Seamus trying to do to that glass of water?
Ron: Turn it to rum. Actually managed a weak tea yesterday, before--
BOOM
Harry: Ron, what's Seamus trying to do to that glass of water?
Ron: Turn it to rum. Actually managed a weak tea yesterday, before--
BOOM
by luvcats222 January 6, 2016
Get the Eye of rabbit, harp string hum, turn this water into rum!mug. 
Refers to da substitute-for-grumbling-at-a delay vocal action dat you engage in while unexpectedly/unavoidably having to wait for something basic or mundane to occur, such as for equipment to warm up, someone to answer da phone, a web-page to load on an internet-computer, etc. Great for when you're either babysitting children (for whom soft singing is often an effectively-calming/soothing way of "placating them for a few" till a desired action/event can happen) or presently have one or more adult-colleagues there who need certain actions and/or information-locating performed on their behalf, and so you are sympathetically showing them dat you hate having to be held up, as well, just da same as they do.
Everyone loves da catchy "Alex Trebek waiting for da contestants to think of an answer" melody, so performing a round of "Jeopardy!" theme humming-on-hold can work wonders to make everyone feel less grumpy/impatient at having to take a little longer than normal for something they want to happen.
by QuacksO December 16, 2023
Get the "Jeopardy!" theme humming-on-holdmug. by Hamsandwihc March 21, 2023
Get the Hummug. 
by Smok710 July 29, 2019
Get the hum strummermug. Something that “hums” is simply something that sucks or that is bad. “Hums” can be used to describe any noun.
by Srew Digel May 27, 2020
Get the Hummug.