Under the Whyte notation system, a duplex steam locomotive that has four leading wheels in a leading truck followed by six coupled driving wheels, a second set with four coupled driving wheels, and four trailing wheels in a trailing truck.

(British) A grade of pencil with lead that makes darker marks than a pencil grade 5B; a pencil with extremely soft lead.

(British) A grade of pencil with lead that makes lighter marks than a pencil grade 5H; a pencil with extremely hard lead. / A pencil of grade 6H.

(statistics mnemonic) The rule stating that a normal distribution will have 68% of its observations within one standard deviation of the mean, 95% within two, and 99.7% within three.

plural of 69

Third-person singular simple present indicative form of 69

(networking) An Internet transition mechanism for migrating from Internet Protocol version 4 (IPv4) to IPv6.

(India) An Indo-Chinese dish consisting of deep-fried chicken and red chillies.

plural of 69er

(often with "the") San Diego (principally its downtown parts), after the 619 area code.