Here’s a word not quite unique to Shakespeare, but you won’t find it in use too often.
cogitation (n.) IPA Pronunciation: 
thought, contemplation
CASSIUS
Then, Brutus, I have much mistook your passion;
By means whereof this breast of mine hath buried
Thoughts of great value, worthy cogitations.
– Julius Caesar (I.ii)
This word takes some cogitation at first, but it does sort of sound like what it is right? The wheels in your head are turning – cogitation. Perfectly logical, right? If nothing else it will make you sound smarter when you use it.