Normally carts belong on a road, so around or beside a hill perhaps depicts an ENCAMPMENT for a relatively BRIEF TIME or a BATTLE FORMATION by a military force. The meaning has been extended to a BLAST, BURST, GUSH likened to the army's rush with weapons upon a defender, or so say the scholars.
　Alternatively, the sages may have used the left element「slope」here for its similarity in appearance to a human backside, and when used「in rotation with plugged orifice」may better explain the meanings of GUSH, BLAST, BURSTING, and BRIEF TIME. Note that the sages often derided the military as a large release of flatulence, a GUST OF WIND「human backside rotated」into farting position.「Human backsides rotated」also may refer to a DEFENSIVE POSITION, BATTLE FORMATION looking somewhat as might a huddle with everyone facing outward instead of inward in a「rotation of backsides」holding shields in front and overhead to protect against a rain of arrows, a position not well suited for aggression, hence was maintained only for a BRIEF TIME during the GUST of falling arrows.
　While seated, the most comfortable position that allows the free flow of flatulence, is to「rotate the backside」up on to one buttock or the other for a BRIEF TIME, prior to releasing the GUST of BLASTING fart gasses. This FORMATION, POSITIONING has the added benefit of allowing others nearby to assume a DEFENSIVE FORMATION, as well as mitigating the ensuing brown traces normally deposited in one's loincloth…BATTLE FORMATION may be a bit strong though, since a similar response by those around will likely result in only a small WAVE of discharges from each anus at most. Subsequently, defecation becomes much more likely, so the farting SPATE will likely subside after a SHORT DURATION.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: disposition of troops; wave; spate; burst; spell; short period of time; classifier for events or states of short duration
Japanese: battle formation, camp, encampment, position, group, war, campaign, each encampment, strong, fierce, intermittent
Unihan extended: column, row or file of troops
EDRDG: camp; battle array; ranks; position