noun

• (slang) An ear.
• (by extension, graphical user interface) A navigational widget, resembling a physical tab, for switching between documents or sets of controls.
• (graphical user interface) The page or form associated with such a navigational widget.
  "How many tabs are open in your Web browser?"
• (British Army, military slang) A fast march or run with full kit.

verb

• (transitive) To affix with tabs; to label.

noun

• (informal, chiefly Canada, US) A restaurant bill.
  "to pick up the tab"
• (informal, chiefly Canada, US) Credit account, e.g., in a shop or bar; slate.
  "to start a tab"
• (by extension) The cost or bill for anything.
  "Moreover, at a tab of $9 million, the system's price is about $1 million less than a conventional heating-cooling plant […]"
• (computing) A space character that extends to the next aligned column, traditionally used for tabulation.
  "No no no no I don't, it's not hate, hate is a strong word, truth be told I do have a slight preference for tabs but that's only because I'm anal and because I prefer precision."

verb

• (computing) To use the Tab key on a computer to advance the cursor or move the input focus, or on a typewriter to advance the carriage.
  "You can prevent a control from getting the focus when the user is tabbing between controls by settings its IsTabStop property to False."