Anticonstitutional (a.)
definition: Opposed to the constitution; unconstitutional.

Anticonstitutional is an 18 letter word that begins with an A and ends in an L

Crystallographical (a.)
definition: Pertaining to crystallography.

Crystallographical is an 18 letter word that begins with a C and ends in an L

Hydrometallurgical (a.)
definition: Of or pertaining to hydrometallurgy; involving the use of liquid reagents in the treatment or reduction of ores.

Hydrometallurgical is an 18 letter word that begins with a H and ends in an L

Lieutenant general
definition: An army officer in rank next below a general and next above a major general.

Lieutenant general is an 18 letter word that begins with an L and ends in an L

Magneto-electrical (a.)
definition: Pertaining to
Or characterized by electricity by the action of magnets; as magneto-electric induction.
Magneto-electrical is an 18 letter word that begins with an M and ends in an L

Mechanico-chemical (a.)
definition: Pertaining to
Connected with or dependent upon both mechanics and chemistry; -- said especially of those sciences which treat of such phenomena as seem to depend on the laws both of mechanics and chemistry as electricity and magnetism.
Mechanico-chemical is an 18 letter word that begins with an M and ends in an L

Parallelogrammical (a.)
definition: Having the properties of a parallelogram.

Parallelogrammical is an 18 letter word that begins with a P and ends in an L

Postmaster-general (n.)
definition: The chief officer of the post-office department of a government. In the United States the postmaster-general is a member of the cabinet.

Postmaster-general is an 18 letter word that begins with a P and ends in an L

Sensori-volitional (a.)
definition: Concerned both in sensation and volition; -- applied to those nerve fibers which pass to and from the cerebro-spinal axis
And are respectively concerned in sensation and volition.
Sensori-volitional is an 18 letter word that begins with an S and ends in an L

Water feather-foil
definition: The water violet (Hottonia palustris); also
The less showy American plant H. inflata.
Water feather-foil is an 18 letter word that begins with a W and ends in an L

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