What is "opus incertum"

Incertum \In*cer"tum\, a. Doubtful; not of definite form.

Opus incertum (Anc. Arch.), a kind of masonry employed in building walls, in which the stones were not squared nor laid in courses; rubblework.

Opus \O"pus\, n.; pl. Opera. [L. See Opera.] A work; specif. (Mus.), a musical composition.

Note: Each composition, or set of pieces, as the composer may choose, is called an opus, and they are numbered in the order of their issue. (Often abbrev. to op.)

Opus incertum. [L.] (Arch.) See under Incertum.

n. (context architecture historical English) An Ancient Roman construction technique, using irregular-shaped and randomly placed uncut stones or fist-sized tuff blocks inserted in a core of ''opus caementicium'' (Roman concrete).

Opus incertum (irregular work) was an ancient Roman construction technique, using irregularly shaped and randomly placed uncut stones or fist-sized tuff blocks inserted in a core of opus caementicium.

Initially it consisted of more careful placement of the coementa (rock fragments and small stones mixed with concrete), making the external surface as plain as possible. Later the external surface became plainer still by reducing the amount of concrete and choosing more regular small stones. When the amount of concrete between stones is particularly reduced, it is defined as opus (quasi) reticulatum.

Used from the beginning of the 2nd century BC until the mid-1st century BC, it was later largely superseded by opus reticulatum.