The aiming and firing of a projectile at a target in line of sight from the weapon.

(algebra) A set of algebraic structures (which are part of a concrete category; e.g., modules) and a set of morphisms between them (e.g., module homomorphisms) which all together form a small category which is the image of a covariant functor whose domain is a directed poset.

(algebra) A set of equivalence classes which partition the disjoint union of the members of a direct system; each equivalence class being a sort of “drainage basin” of the mappings (of the morphisms) of the direct system, if these are analogically considered as “rivers”. (If i<k,j<k in the indexing poset, then there exist f_ik:A_i→A_k and f_jk:A_j→A_k. If a_i∈A_i,a_j∈A_j such that f_ik(a_i)=f_jk(a_j) then a_i∼a_j. If k = j then f_jj(a_j)=a_j,f_ij(a_i)=a_j.)

The practice, of cats and some other animals, of placing their hindfeet in the same place as (i.e. in the prints left by) their forefeet.

Used other than figuratively or idiomatically: see direct, access. / (computing) Synonym of random access

(politics) Form of democracy in which people decide on policy initiatives directly, without electing representatives.

Alternative form of business-to-consumer

plural of airworthiness directive

Focused on reaching a particular objective or serving a particular purpose.

(aviation, law) A regulation issued by the civil aviation authority of a country or region, generally in response to the discovery of an unsafe condition affecting particular aircraft, requiring that certain actions (such as specified modifications or enhanced maintenance or inspection requirements) be performed on these aircraft in order for them to remain legally airworthy.