acumminate doubles the m after the stress
stress-doubleA doubled consonant is the standard English signal for a short stressed vowel. Acuminate has a long stressed vowel and no doubled consonant anywhere in it.
heard asacumminate
spelledacuminate
saiduh-KYOO-min-ut
The spelling is acuminate, with one m.
Stress lands squarely on the syllable before this m, and doubling after a stressed syllable is such a reliable English habit that the hand does it without being asked. Hammer, summer, common. What blocks it here is the length of the vowel: KYOO is long, and a long vowel takes a single consonant after it.
Filed alongside
acumanate acuminnate accuminate acumunate acyouminate acyoominate
All of them are filed together. All 7 spellings of acuminate.