Wiktionary
haboku
n. A technique of using splashed ink in brushwork painting, especially for painting a landscape.
Wikipedia
Haboku
and are both a technique employed in suiboku (ink based), as seen in landscape paintings, involving an abstract simplification of forms and freedom of brushwork. The two terms are often confused with each other in ordinary use. Generally, haboku relies on a layered contrast black, gray and white, whereas hatsuboku utilizes "splashes" of ink, without leaving clear contours or outlines. In Japan, these styles of painting were firmly founded and spread by the Japanese painter Sesshu Toyo.