guesstimate

or gues·ti·mate

[ verb ges-tuh-meyt; noun ges-tuh-mit, -meyt ]
/ verb ˈgɛs təˌmeɪt; noun ˈgɛs tə mɪt, -ˌmeɪt /
Informal.

verb (used with object), guess·ti·mat·ed, guess·ti·mat·ing.

to estimate without substantial basis in facts or statistics.

noun

an estimate arrived at by guesswork.

Origin of guesstimate

1935–40, Americanism; blend of guess and estimate

British Dictionary definitions for guesstimate

guesstimate

guestimate

/ informal /

noun (ˈɡɛstɪmɪt)

an estimate calculated mainly or only by guesswork

verb (ˈɡɛstɪˌmeɪt)

to form a guesstimate of