OBSERVATION 1 . Action and effect of OBSERV, look something with arrest, be attentive to something. 2 . Do scientific research on something: astronomers observe nebulae and galaxies with great detail. 3 . Respect a day or a norm or precept as part of the religious cult professed by a parishioner or believer. 4 . Written note or comment on a written or printed letter, for reading by third parties. 5 . Report that the inspector or teacher makes about a student in the school's class or behavior book.