As a mass noun: strength of character or purpose; courage, boldness, assertiveness. Cf. spirit, n. 6. Now rare (chiefly Scottish, archaic, or poetic…

Over-readiness, presumptuous self-confidence; hence, lack of becoming modesty, boldness.

The action of perk, v.2 (in various senses); erectness; a lively, jaunty, or flirtatious bearing; proud or conceited behaviour.

Offensive presumption or temerity.

Self-assurance, presumption.

Scottish. Self-assertion, self-confidence, pride.

The action or fact of asserting one's status, individuality, rights, opinions, etc.

The quality of being irritatingly self-assertive or conceited.

The quality of being cocky; arrogant or conceited behaviour or demeanour; brash or excessive self-confidence.

The quality of being perky (in various senses).

self-assertive character or quality.

self-importance, arrogance; brashness, impudence.

U.S. Obtrusive behaviour.

Tendency towards assertion or self-assertion.

Originally U.S. Feeling or energy displayed in asserting oneself, or in showing drive or initiative; aggressiveness, assertiveness, forcefulness…

The state or quality of being ‘pushy’; excessive or aggressive self-assertion.

the condition or quality of being chesty (in any of the senses above).

Hence, any highly independent or individual outlook, approach, appearance, etc.; self-possession; style, swagger, front; esp. in with (an) attitude…