But (not that you asked) from my observations, an orgasm feels different from man to man too.  Sometimes it appears to be a mild, "Oh, yeah... that was good", with some men I really can't tell there's so little outward physical sign of it,  while others appear to almost be in pain at that moment with their entire bodies convulsing at that moment.  

For me personally, my orgasms are like snowflakes: no two are exactly the same.  Each one is a little bit different.  And I have orgasms from both vaginal and clitoral stimulation but I do not squirt; I'm also easily orgasmic (that's a real medical thing) and can "get there" from my neck being nibbled in just the right way.  Honest.

However, many women profess to reaching orgasm only from clitoral stimulus and some medical professionals claim that is the only way a woman can reach orgasm.

What does it feel like when a man comes in my mouth?   Well, again, each one is slightly different: some guys just dribble, others are shooting for distance; sometimes it feels lukewarm while other times it is almost scalding hot.  
But basically, if you really want to get an idea of the sensation, get a Jello Shot Syringe (don't know what that is? I included a link!) filled with Jello.... warm it up in the microwave just enough so that it is now a thick viscous liquid, and squirt that into your mouth.  How do I know this?  Well, it involves tailgating at a Jimmy Buffett concert on a very warm day.... and that's all I have to say about that.  

Where do I want you to touch?  Well, I like being touched all over but wherever you touch, I like it soft and gentle.  But not barely-touching-feels-like-cobwebs-touches. LOL.  
Please don't use your fingernails, and if you're "touching" me with your lips: NO TEETH!  

 
See?  We women are complicated.

I too hope to increase my understanding of women.  I've asked many ladies what their orgasm feels like but have not received any answers beyond "great" or some such.  They seem to vary so much between women.  Sometimes they are barely noticeable to me, and I have to ask if they have cum.  Others are seismic  events that take geologic eons to work up to and then have earthshaking results.

at my age I have had a lot of orgasms and yet I would be hard-pressed to describe one. Written words don't exist that would allow another person to experience the physical and psychological sensations brought on by glorious fuck or blowjob..

I'm amazed at how much I continue to learn about my own body and responses. I dove into a practice called "orgasmic meditation". In this ritual, the woman disrobes from the waist down lays on her back and butterflies her legs open. The man pulls back the hood of the clit and in a very specific way strokes the clit for fifteen minutes. The practice is enlightening on both sides. The clit is a galaxy when explored in this very special way. The sensations are amazing... different than anything I've felt. The more you practice, the stranger, deeper and more intense it gets.

You can't fake it on your own, though. You have to get trained by someone who knows what they are doing. It is impossible for the woman receiving to give instruction. Must have a coach the first time.  

Kudos for continuing to ask and learn. Likewise, I continue to ask and learn. I took a one week intensive on Tantra and picked up some things you don't learn "on the street".

Link to YouTube video on subject...