The difference between Impale and Picket

Impale as a verb (transitive):

To pierce (something) with any long, pointed object.

Impale as a verb (transitive, heraldry):

To place two coats of arms side by side on the same shield (often those of two spouses upon marriage).

Impale as a verb (ambitransitive):

To pierce with a pale; to put to death by fixing on a sharp stake.

Impale as a verb (ambitransitive):

To enclose or fence with stakes.

Picket as a noun:

A stake driven into the ground.

Picket as a noun (historical):

A type of punishment by which an offender had to rest his or her entire body weight on the top of a small stake.

Picket as a noun:

A tool in mountaineering that is driven into the snow and used as an anchor or to arrest falls.

Picket as a noun (military):

One of the soldiers or troops placed on a line forward of a position to warn against an enemy advance; or any unit (for example, an aircraft or ship) performing a similar function.

Picket as a noun (sometimes, figurative):

A sentry.

Picket as a noun:

A protester positioned outside an office, workplace etc. during a strike (usually in plural); also the protest itself.

Picket as a noun (card games, uncountable):

The card game piquet.

Picket as a verb (intransitive):

To protest, organized by a labour union, typically in front of the location of employment.

Picket as a verb (transitive):

To enclose or fortify with pickets or pointed stakes.

Picket as a verb (transitive):

To tether to, or as if to, a picket.

Picket as a verb (transitive):

To guard, as a camp or road, by an outlying picket.

Picket as a verb (obsolete, transitive):

To torture by forcing to stand with one foot on a pointed stake.