Stiff, rigid, inflexible, tense, stark, wooden can mean so firm, hard, or tough in texture, consistency, or quality as to be impossible or highly difficult to bend or enliven.
Stiff, the most common word of this group, is applicable where this condition exists in any noticeable degree; it may describe either a desirable or an undesirable quality, because, except in its extended senses, it merely implies a condition and carries neither depreciative nor commendatory connotations.
In its extended senses stiff , when applied to persons or their manners and their expression, usually suggests either extreme formality and coldness or a lack of ease, grace, or graciousness in dealing with others.
When applied to something that must be overcome or must be accomplished, the term implies unusual difficulty or the need of great exertion and when applied to something that under particular circumstances or in a particular case has lost its usual or typical pliancy or pliability, stiff implies difficulty (as in using, moving, or handling).
In a variety of other senses, stiff implies harshness or extreme severity or great strength or violence.
Rigid ((for extended senses see RIGID 2 )) implies so high a degree of stiffness that the thing so described cannot be bent or flexed without breaking it.
Inflexible (for extended sense see INFLEXIBLE 2 ) differs from rigid only in suggesting a lack of limberness or an incapacity for being bent rather than a texture or consistency that resists bending or deforming. Consequently it is often used when a less precise term is needed and merely an approach to rigidity is suggested.
Tense (see also TIGHT 1 ) occurs especially in reference to bodily structures (as muscles, fibers, or membranes) that are stretched so tight, or so strained by effort or excitement, that they have lost their elasticity or flexibility either for the time being or permanently.
Stark usually suggests a stiffness that is associated with loss of life, warmth, power, vitality, or fluidity and therefore often also connotes desolation, barrenness, death, or present valuelessness; frequently it is accompanied by stiff or rigid .
Often stark is merely an intensive (often an adverb) meaning little more than such as is stated or described without qualification.
Wooden suggests not only the hardness and inflexibility of wood but its dryness and its lack of suppleness and plasticity; consequently the term suggests not only stiffness and lack of life and grace but often clumsiness or deadness or heaviness of spirit.