1. （意见等）令人不快的，难以接受的
If you describe an idea as unpalatable, you mean that you find it unpleasant and difficult to accept.

2. 难吃的；不可口的
If you describe food as unpalatable, you mean that it is so unpleasant that you can hardly eat it.

1. not pleasant or acceptable to the taste or mind

e.g. an unpalatable meal
unpalatable truths
unpalatable behavior