sweeper,.hack, hack away, hacker, put one's foot down

Elon Musk is putting his foot down.

Tesla Slaps Down Model 3 Speculators, Cancelling Excess Reservations

After some broke the 2-preorder limit, Elon Musk quickly put his foot down.

FOR.TN

Google-Hacking Goes To China

Hack has several meanings in the technology and computer science fields: a clever or quick fix to a computer program problem; a clumsy or inelegant solution to a problem; or a modification of a program or device to give the user access to features that were otherwise unavailable to them.

The California Secretary of State has invited Black Box Voting to hack away at
some Diebold voting systems. The testing is set for Nov. 30, 2005.

這詞 hack away還不太清楚
另一例
Even though it was Sunday, the train was crowded and many people were standing. A young man, holding on to an overhead strap, coughed without covering his mouth. The poor person sitting in front of him literally got sprayed liberally from above.
An elderly man, sitting at the end of a seat inside the compartment, started hacking away. He, too, did not cover his mouth, so his germs, too, must have traveled quite a distance. The mist-like spray of saliva is invisible, but is said to travel a few meters.

...

Another Vintage Point

Rolls-Royce homemade street sweeper, 1930s.

sweeper 
noun [C]
1 someone or something that sweeps:
a carpet sweeper (= a machine for cleaning carpets)
a road sweeper (= a person whose job is cleaning the roads)

2 In football, a sweeper is a player whose position is behind the other defenders (= players whose main aim is to stop points from being scored). Platt was twice hacked down in the second half by the other team's sweeper.

hack (CUT)
verb
1 [I or T; + adverb or preposition] to cut into pieces in a rough and violent way, often without aiming exactly:
Three villagers were hacked to death in a savage attack.
Don't just hack (away) at the bread - cut it properly!
The butcher hacked off a large chunk of meat.
FIGURATIVE The article had been hacked about (= carelessly changed) so much it was scarcely recognizable.

2 [T usually + adverb or preposition] UK in football and rugby, to kick the ball away or to foul (= act against the rules) by kicking another player in the leg:
Platt was twice hacked down in the second half by the other team's sweeper.

Hacking : the art of exploitation / by Jon Erickson
Erickson, Jon (Jon Mark), 1977-
San Francisco : No Starch Press, c2003

hack¹

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━━ v. 切る, たたき切る; 切り刻む; 切りつける ((at)); 切り開きながら進む ((through)); 台なしにする, （文章を）ずたずたにする ((about)); （土地を）耕す; 【ラグビー】（相手選手の）向こうずねを蹴(け)る; 【バスケット】（相手選手の）ボールを持つ腕を打つ; 〔俗〕 うまくやらかす; 空咳(からせき)をする; 【コンピュータ】（プログラムを）巧妙に改変する［して楽しむ］.
hack around　〔米話〕 時間をむだに過ごす.
hack away at　…に（何度も）切りかかる.
hack it　〔俗〕 うまくやり抜く.
━━ n. たたき切る［切り刻む］こと; 刻みあと, 切り目; 傷; 刃物; おの; 空咳; 【ラグビー】（向こうずねを）蹴ること; 【バスケット】ハッキング.
hack・er　━━ n. 〔話〕 【コンピュータ】ハッカー, コンピュータマニア; へたくそな人.
hack・ing　━━ n. 【コンピュータ】（マニア的な）コンピュータいじり.
hack・saw　（金属切断用の）弓のこ.

━━ n. 貸馬; 貸馬車; 〔話〕 タクシー; 乗用馬; 老馬; 三文文士; 〔英〕 三流政治家; （普通単数形で） 難儀な旅.
━━ vt. （馬を）乗用に貸す; 使い古す.
━━ vi. 馬に乗って行く ((along)); タクシーを運転する; 下働きする.
━━ a. 報酬目当ての, 売文の; 退屈な, 古臭い.
hacking jacket　乗馬用の上着.
hack pack　ジャーナリスト連中.
hack・work　つまらぬ［下請け］仕事; （金目当ての）雑文書き.

put one's foot down

informal

1Adopt a firm policy when faced with opposition or disobedience.

Example sentences

2British Accelerate a motor vehicle by pressing the accelerator pedal.