Lowball is an early type of railway signal

Railway signal

A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal's indication and acts accordingly...

 indicating danger/stop. The ball signal was a light or indicator suspended from a rope, that could move upwards and downwards, held by a weighted ball. The lowball signal was indicated when the weighted ball, and therefore signal, was at the end of its rope in the low position, indicating stop.

It can also refer to:

• Low-ball
  Low-Ball
  The low-ball is a persuasion and selling technique in which an item or service is offered at a lower price than is actually intended to be charged, after which the price is raised to increase profits....
  
  , a persuasion technique
• Lowball (poker)
  Lowball (poker)
  Some forms of poker, often called lowball, sometimes called low poker, reward poor poker hands . There are four common variations on this idea, differing in whether aces are treated as high cards or low cards, and whether or not straights and flushes are used. The methods are:* Ace-to-five low:...
  
  , a variant of the card game poker, in which hand values are reversed so that the lowest-valued hand wins
• Lowball estimate, also known as cost underestimation, the estimation of the lower bound of a venture's cost
• Lowball glass
  Old fashioned glass
  The Old Fashioned glass, lowball glass, or rocks glass is a short tumbler used for serving an alcoholic beverage, such as whisky, with ice cubes...
  
  , a short glass tumbler used for serving certain varieties of alcoholic beverage
  Alcoholic beverage
  An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...