"Non gli piaccio."
"piacere" is rather unusual. The sentence above is literally "To him I am not pleasing."
Thanks for the links but it still doesn't explain the presence of "gli" as a plural masculine form... Even following the indirect sense of piacere usage, "I am not pleasing to him" should technically be "non lui piaccio"... Consequently, "non gli piaccio" should be "I am not pleasing to them"... Right?
No. "gli" is "to him" or "for him". It's an indirect object pronoun. "gli" is also the masculine plural article "the", which is probably where the confusing is coming from. Similarly, "le" is the indirect object pronoun meaning "to her", "mi" is "to me", etc. "gli piaccio" = "he likes me (I am pleasing to him)", "le piace la torta" = "she likes the cake (the cake is pleasing to her)", "mi piace" = "I like it (it is pleasing to me)".
Wow,was this one strange! Before trying to answer, I clicked on the new verb and it gave the definition as 'like oneself'. It didn't seem right, and I sure couldn't see where gli fit in, as we had only seen 'gli' as the plural masculine article, but my best guess was therefore ' I do not like myself'. I wasn't even in the ballpark! :)