Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. collīsus (conl-), a, um, Part., from collido.
2. collīsus (conl-), ūs, m. [collido], a striking together, collision (very rare): margaritarum, Plin. 9, 35, 56, § 114: dentium, Cael. Aur. Acut. 2, 12.