hydrant

As a letter s

is the letter s with a.

As a noun hydrant is

fire hydrant.

As nouns the difference between hydrant and hose

is that hydrant is fire hydrant while hose is trousers.

As a noun hydrant

is fire hydrant.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between spigot and hydrant

is that spigot is a pin or peg used to stop the vent in a cask while hydrant is an outlet from a liquid/fluid main often consisting of an upright pipe with a valve attached from which fluid (e.g. water or fuel) can be tapped.

As nouns the difference between hydrant and hydrogen

is that hydrant is an outlet from a liquid/fluid main often consisting of an upright pipe with a valve attached from which fluid (e.g. water or fuel) can be tapped while hydrogen is the lightest chemical element (symbol H) with an atomic number of 1 and atomic weight of 1.00794.

As nouns the difference between hydrant and tub

is that hydrant is fire hydrant while tub is a flat-bottomed vessel, of width similar to or greater than its height, used for storing or packing things, or for washing things in.

As a verb tub is

to plant, set, or store in a tub.