[French trimestre, from Latin trimēstris, trimēnstris, of three months : tri-, tri- + mēnsis, month.]trimestral tri·mes'tral (-trəl) or tri·mes'tri·al (-trē-əl) adj.
[Etymology: tri + Lat: ‘month’] time Any three-month period, usually a subdivision of a greater period that is a multiple of such, particularly the successive parts of the nine-month period of human gestation. Used erroneously for any period that is a third of some year, e.g. with a year-round school scheme having three four-month terms.
A period of 3 months.
One of the three periods of approximately 3 months each into which pregnancy is divided.