1. in a manner showing lack of education or inability to read and write
2. in a way that is ignorant or uninformed about a particular subject

Examples

• He spoke illiterately, struggling to form complete sentences.
• The article was written illiterately, full of grammatical errors and poor spelling.
• She commented illiterately on the scientific study, revealing her lack of understanding.
• The document was signed illiterately, with an unsteady mark instead of a proper signature.
• He expressed himself illiterately, using crude language and broken English.