The vowel before the t is an a
schwaThree of the five vowels in lanceolate are unstressed. The ear gets a blur and the fingers pick a letter.
heard aslanceolute
spelledlanceolate
saidLAN-see-uh-layt
lanceolate. The ending is -ate.
Every shape word in this section takes the same Latin -atus, and English lands it as -ate: cuneate, acuminate, lanceolate. Once the stress has moved off, that a is barely a vowel at all, which is how it comes out as a u.
Also filed here
lanceulate lanseolate lanceollate lanceolat lanceelate lancealate
Each one has a page of its own. All 7 spellings of lanceolate.