When you forget what a word is

I sometimes take my shower with the light off  because it's a fun sensory deprivation thing, forcing yourself to concentrate on where everything is in a pitch black windowless room. And it's quite a mental challenge and when you come out you feel really awake. Today I was doing this when I totally forgot what the word for 'altruism' was. I thought it might have been 'altruousness' or 'altruicity'.

I will tell you now: standing naked under a jet of water in total darkness, one's grip on reality is tenuous. I actually had to reach out of the cubicle and put the light on at this point, and upon being able to see again remembered it was an -ism and not an -icity.

This sort of thing happens to me every once in a while. About a year ago I realised I had no idea what the word 'ubiquitous' meant. I wasn't even sure if I had once known it and subsequently forgot, or if I was just having a sudden realisation about a gap in my vocabulary.

Dear readers, I have been told by someone that I should try to increase the audience participation side of things on here, so I'm opening the floor to comments. Have you ever forgot what a word means? If so, what was that word? Answer me. Yeah.