source: [水飲み鳥のような第七使徒が激しく攻撃されるGIF画像｜無料GIF画像検索 GIFMAGAZINE 103233]

1. concentrated on a single area or subject or into a short time; very thorough or vigorous:

集中的な〈講座･訓練など〉; 徹底的な, 激しい

e.g. she undertook an intensive Arabic course

e.g. eight days of intensive arms talks.

(of agriculture) aiming to achieve the highest possible level of production within a limited area, especially by using chemical and technological aids:

集約的な

e.g. intensive farming. Often contrasted with extensive (sense 2) .

usually in combination (typically in business and economics) concentrating on or making much use of a specified thing:

e.g. computer-intensive methods.

2. Grammar (of an adjective, adverb, or particle) expressing intensity; giving force or emphasis.

〘文法〙 強意, 強調の

3. chiefly Physics denoting a property which is measured in terms of intensity (e.g. concentration) rather than of extent (e.g. volume), and so is not simply increased by addition of one thing to another.

noun Grammar

an intensive adjective, adverb, or particle; an intensifier.

intensiveness noun

late Middle English (in the sense ‘vehement, intense’): from French intensif, -ive or medieval Latin intensivus, from intendere (see intend).

On the difference between intensive and intense, see usage at intense.