As nouns the difference between assertation and assertion

is that assertation is an assertion, statement of opinion while assertion is the act of asserting, or that which is asserted; positive declaration or averment; affirmation; statement asserted; position advanced.

As verbs the difference between surfboard and skurf

is that surfboard is to use a surfboard; to surf while skurf is to ride on a small surfboard towed behind a speedboat, after the manner of water skiing.

As a noun surfboard

is a shaped waterproof plank, usually made of wood or foam and reinforced plastic, used to surf on waves.

Gyrodyne is a see also of rotorcraft.

As a noun rotorcraft is

any aircraft that obtains its lift from rotors.

As nouns the difference between helicopter and rotorcraft

is that helicopter is an aircraft that is borne along by one or more sets of long rotating blades which allow it to hover, move in any direction including reverse, or land; and having a smaller set of blades on its tail that stabilize the aircraft while rotorcraft is any aircraft that obtains its lift from rotors.

As a verb helicopter

is to transport by helicopter.

Tiltrotor is a see also of rotorcraft.

As nouns the difference between tiltrotor and rotorcraft

is that tiltrotor is an aircraft that has powered rotors mounted on engine pods that can rotate to provide lift and/or propulsion while rotorcraft is any aircraft that obtains its lift from rotors.

As nouns the difference between flay and flayer

is that flay is a fright; a scare while flayer is one who or that which flays.

As a verb flay

is to cause to fly; put to flight; drive off (by frightening) or flay can be to strip skin off.

As an adjective unsubstantial

is (archaic).

As an adverb unsubstantially is

in an unsubstantial way.

As adjectives the difference between ruthless and gangsterlike

is that ruthless is without pity or compassion; cruel, pitiless while gangsterlike is resembling a gangster or some aspect of one; criminal, ruthless, etc.

Gangsterlike is a synonym of gangsterish.

As adjectives the difference between gangsterish and gangsterlike

is that gangsterish is gangsterlike while gangsterlike is resembling a gangster or some aspect of one; criminal, ruthless, etc.

As a noun biscuit

is (lb) a cookie.

As an adjective biscuitlike is

resembling a biscuit or some aspect of one.