agar

noun

ˈä-gər 

1

or less commonly agar-agar

ˌä-gər-ˈä-gər 

or agar agar : a gelatinous colloidal extract of a red alga (as of the genera Gelidium, Gracilaria, and Eucheuma) used especially in culture media or as a gelling and stabilizing agent in foods

Use agar-agar (also called agar …) to make savory aspics, fruit-filled dessert molds, and smooth pudding and pie fillings.

—Susan Jane Cheney

One of the first gelling agents used in culture media was gelatin. The problem with this gelling agent is that it melts at 37°C, which is the incubation temperature of most bacteria. … Agar was then used in culture media.

—M. Bonnet et al.

2

: a culture medium containing agar

For detection of hemolysis, bacteria were grown on … agar …

—Sudip Das et al.

an agar medium

Examples of agar in a Sentence

Recent Examples on the Web

The team printed colonies onto agar with about 5 millimeters separating neighboring cells. — Aamir Khollam, Interesting Engineering, 18 Aug. 2026

Tissue culture is a cloning process where, for orchids, shoot tips and axillary or side buds are sterilized and placed on agar — a jelly-like material that hardens into a firm gel — that contains plant nutrients and hormones. — Joshua Siskin, Oc Register, 14 May 2026

Instructions In a small skillet over medium heat, stir together the agar and 3 tablespoons of water until dissolved. — Yoko Lamn, Saveur, 23 Apr. 2026

The studio’s bio-plastics are built from biopolymers such as agar and gelatin, with varying components used to control flexibility and translucency. — Angela Velasquez, Sourcing Journal, 30 Jan. 2026

Word History

Etymology

short for Malay agar-agar, name for the red alga from which it is extracted

First Known Use

1885, in the meaning defined at sense 1

Phrases Containing agar

• agar plate

Rhymes for agar

• gager
• jager
• sager
• vaguer

Kids Definition

agar

noun

ˈäg-ər 

variants also agar-agar

ˈäg-ə-ˈräg-ər

1

: a jellylike substance obtained from a red alga and used especially in culture media or to give firmness to foods

2

: a culture medium containing agar

Medical Definition

agar

noun

ˈäg-ər 

1

: a gelatinous colloidal extract of a red alga (as of the genera Gelidium, Gracilaria, and Eucheuma) used especially in culture media or as a gelling and stabilizing agent in foods

2

: a culture medium containing agar