To stay in order, be obedient.
Origin: From the line in the House of Commons which members must stay behind during session. "Toe the line" is to conform to the rules.
To behave according to strict rules. Sometimes an order given, especially to a child.
Somewhat archaic.
Angry father: "You'd better toe the line this time, mister, or next time I catch you tattooing your sister's name on shaved dogs you'll be grounded for a month!"
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".