Something easy, not difficult, not posing problems.

certainly, sure (said when granting a request) / no thanks is necessary; you're welcome (said in response to an expression of gratitude)

(military) The ground between trenches where a soldier from either side would be easily targeted.

(geology) a concretion of oxides of manganese and iron found on the floor of many oceans

plural of persona non grata

(idiomatic, slang) Not a big deal, not something to worry about.

(slang) Expressing firm disagreement.

(physics) a fluid whose stress at each point is not linearly proportional to the strain rate at that point; i.e. its viscosity depends on the applied shear force

(chemistry) Any chemical compound in which the number of atoms of each element is not expressible as the ratio of small integers; normally due to missing atoms in a solid state lattice.

(US, chiefly Southern US) Any biting midge (family Ceratopogonidae), small flies (1–4 mm long); sometimes the species Leptoconops torrens in particular.