Here are a few examples:
Technical terms:
* Incomprehensibilities (8 syllables)
* Electroencephalography (7 syllables)
* Antidisestablishmentarianism (10 syllables - though this is a notorious example, often used in debates about long words)
Uncommon words:
* Pneumonoultramicroscopicsilicovolcanoconiosis (45 syllables) - This is considered the longest word in the English language, though it's not a real word in the sense of being commonly used. It was coined in 1935 as a humorous example of a very long word.
It's worth noting that these examples are rare exceptions. Most words in everyday use have far fewer syllables.