Conspiracy theories (CTs) are spectacular narratives, widely spread, that pose societal threats. We test whether CTs might be linguistically creative products, which would facilitate their transmission and thereby account for their widespread popularity. We analyzed nominal compounds (e.g., mind control, carbon dioxide; N = 1,713,568) from a large corpus of conspiracist and mainstream texts matched by topic. In conspiracist texts, compounds showed greater originality, divergence, and sophistication, but they were used with lower frequency and were more often repeated in different contexts. This pattern suggests a creative aspect in the generation of compounds, coupled with rigidity in their use. We interpret these findings as an effect of loosely defined conceptual boundaries among conspiracist writers, in conjunction with social functions like status or group signaling. Our findings not only contribute to the discourse on creativity in CTs but also provide insights into the communicative advantage of CTs.