incapable of or resistant to bending; "a rigid strip of metal"; "a table made of rigid plastic"; "a palace guardsman stiff as a poker"; "stiff hair"; "a stiff neck"
designating an airship or dirigible having a form maintained by a stiff unyielding frame or structure
characterized by forceful and energetic action or activity; "a vigorous hiker"; "gave her skirt a vigorous shake"; "a vigorous campaign"; "a vigorous foreign policy"; "vigorous opposition to the war"
strong and active physically or mentally; "a vigorous old man who spent half of his day on horseback"- W.H.Hudson
be sufficient; be adequate, either in quality or quantity; "A few words would answer"; "This car suits my purpose well"; "Will $100 do?"; "A 'B' grade doesn't suffice to get me into medical school"; "Nothing else will serve"
accept (someone) to be what is claimed or accept his power and authority; "The Crown Prince was acknowledged as the true heir to the throne"; "We do not recognize your gods"
accept as legally binding and valid; "acknowledge the deed"
express obligation, thanks, or gratitude for; "We must acknowledge the kindness she showed towards us"
report the receipt of; "The program committee acknowledged the submission of the authors of the paper"
not changeable or subject to change; "a fixed and unchangeable part of the germ plasm"-Ashley Montagu; "the unchangeable seasons"; "one of the unchangeable facts of life"