* Words can be combined: Portuguese, like many languages, allows for compound words. You can combine multiple words to create even longer ones. For example, you could theoretically create a word like "anticonstitucionalissimamente" (meaning "unconstitutionally") and then add more prefixes and suffixes to make it even longer.
* Longest word is subjective: What constitutes a "word" can be debated. Do you count technical terms or words used only in specific fields?
So, there's no definitive answer. But some of the contenders for longest "common" words in Portuguese include:
* Pneumoultramicroscopicsilicovolcanoconiosis: This is a real, though rarely used, word referring to a lung disease caused by inhaling very fine silica dust.
* Antidisestablishmentarianism: This word comes from English, but is sometimes used in Portuguese as well.
* Floccinaucinihilipilification: Another English word adopted by Portuguese, meaning "the act of estimating something as worthless."
Ultimately, the "biggest" Portuguese word depends on what you consider a "word" and how creative you want to get with combining them!