noun, masculine/feminine/sɑ̃.de.sɛ̃/plural: sans-desseins
sans-dessein is masculine or feminine depending on context in French.
a person who is stupid, clumsy, or literally cannot plan ahead
“À moins qu'un sans-dessein sur Twitter aille dire que le gouvernement fait de la bonne ouvrage.” — Unless an idiot on Twitter is going to say that the government did a good job.
Literally, “without plan”.