Muscle Terms

Size

Brevis - short
Longus - long
Maxiumus - large
Minimus - small
Vastus - huge

Shape

Deltoid - triangular
Latissimus - wide
Rhombus - rhomboid
Teres - round
Trapezius - trapezoid

Location

Brachii - arm
Gluteus - buttock
Infra - below
Intermedius - in between
Lateralis - lateral
Medialis - medial
Pectoralis - chest
Sub - deeper
Supra - above

Direction of Muscle Fibers

Oblique - angular
Rectus - straight

Action

Abductor - moves part away from midline
Adductor - moves part toward midline 
Depressor - depresses
Extensor - extends
Flexor - flexes
Levator - elevates

Dealing with Numbers

Biceps - two points of attachment
Triceps - three points of attachment
Quadriceps - four parts

Other Terms Dealing with Muscles

Aponeuroses - thick fibrous sheets that can connect muscle to the periosteum of a bone or other tendons
Fascia - dense connective tissue that holds muscle in position and separates them from adjacent muscles