hypothesize UK /haɪˈpɒθ.ɪ.saɪz/US /haɪˈpɑ.θəˌsaɪz/ verb1 •To assume or assert tentatively on uncertain grounds.When hormones signal breast cells to divide more rapidly, scientists hypothesize, they increase breast cancer risk by causing precancerous or cancerous cells to multiply. — 1996 formshypothesized · hypothesizing · hypothesizes