What is the meaning of Sub-lieutenant?

A commissioned officer of the navy whose rank is immediately below that of a lieutenant.

  1. A commissioned officer of the Royal Navy ranking above a midshipman and below a lieutenant.
  2. A commissioned officer of the navy ranking above an acting sub-lieutenant and below a lieutenant.

A commissioned officer of the Royal Navy ranking above a midshipman and below a lieutenant.

A commissioned officer of the navy ranking above an acting sub-lieutenant and below a lieutenant.

Source: wiktionary.org