n. 1 the act or an instance of noticing; the condition of being noticed. 2 perception; the faculty of taking notice. 3 a remark or statement, esp. one that is of the nature of a comment. 4 a the accurate watching and noting of phenomena as they occur in nature with regard to cause and effect or mutual relations. b the noting of the symptoms of a patient, the behaviour of a suspect, etc. 5 the taking of the sun's or another heavenly body's altitude to find a latitude or longitude. 6 Mil. the watching of a fortress or hostile position or movements. observation car esp. US a carriage in a train built so as to afford good views. observation post Mil. a post for watching the effect of artillery fire etc. under observation being watched. observational adj. observationally adv.
[ ME f. L observatio (as OBSERVE) ]