This is a catalog record for a hiccup

150 $a Hiccups
450 $a Hiccoughing
450 $a Hiccoughs
450 $a Hiccuping
450 $a Hiccupping
450 $a Singultus
550 $w g $a Spasms
550 $w g $a Symptoms
670 $a Web. 3 $b(hiccup or hiccough; hiccuping also hiccupping, hiccoughing)

I found this in the Library of Congress Subject Headings search, and felt a little deflated.  It's been done, well of course it's been done. 

BUT what hasn't been done, it seems, is the cataloging of an INDIVIDUAL hiccup. 

I spent about an hour going through the fields and subfields and delimiters trying to decipher it all.  It isn't available in one place.  To find out what the 670 field was I went to The United Nations website (because I googled "MARC tag 670") which told me what it was (the source of the information on this particular item we are speaking of in field 100) but then I had to go to  Library of Congress via the UN site because when I searched the LOC in a general kind if manner I got this response about the 670 field:
 
659 - 679 unassigned  (you'd think the LOC wouldn't contradict itself.  Or maybe I am missing something.  I hope it is that, that i am simply dumb and/or impaired because if the LOC is confused then we're all going to hell in a handbasket)
 
So eventually I was able to figure out what 670 is.

Now there was the questions of what the two 550 fields were (550 being the "issuing body note", that is, a note from the person who cataloged it.  I think.) and what did the subfield $wg mean?  For that I went to this part of the LOC which WOW! Had nothing to say about the $w subfield.  Surprise!

Somehow I found LOC Tracings which finally told me that $w means a control subfield (which you don't really have to understand) and that $wg means that the word following it is a Broader Term.  Which makes sense, spasms are a broader term for hiccups.  If there was a narrower term it would be shown as $wh.  And then the next subfield within that 550 field, immediately following the $wg is $a The Broader Term itself.

You can also use $wd to show the acronym (I don't think there is one for hiccups), $wa for an earlier heading, maybe $aHonkHonk, and then $wb for a later term like, $aHOoOOoOoo. 
You would use these subfields if in the past we refered to and cataloged hiccups as HonkHonks and in the future (I guess you would have to add this to the record later) they are known as HOoOOoOoos.  That's in the future, when we mix capital and lowercase letters to indicate an entire additonal 26 character alphabet with perhaps currently unpronounceable sounds. 
If you have read this far then you are either a cataloger or you are truly my friend.