A firm stance or policy on which one will not compromise

(genetics) A triangular graphical representation of linkage disequilibrium in which different colours represent different magnitudes of linkage between pairs of loci

(genetics) A non-random association of two or more alleles at two or more loci; normally caused by an interaction between genes, and often illustrated on a pairwise linkage disequilibrium diagram (HapMap)

(mathematics) Equal to a sum of finitely many linear functions, each defined on a convex polytope: said of functions between vector spaces

(topology) A link with a standard projection comprising several tangles, each a braid on two strands, with the tangles arranged in some cyclic order.

(idiomatic, often used attributively) The worst or lowest quality on the market, especially among a range of products.

(nautical) A mark on the hull of a merchant ship to show the waterline under specified conditions, indicating the maximum load that the ship may carry.

(mathematics) The real number system, viewed as a line.

(IRC) The line in an IRCd configuration file that records the hostname of a banned user

(transitive, IRC) To ban a user from a server