Flutter. Hover, flap, flirt; palpitate, tremble; flaunt; fluctuate, waver, oscillate, vacillate, be inconstant, be unsteady; flit, quiver, flicker.
Ant. Perch, roost, nestle, settle, subside, collapse, rest, repose, pause, sink, lull.
Flux. Flow, flowing; mutation, change, shifting, transition; fusion, melting; solvent; motion, progression, substitution, transmutation.
Ant. Stagnation, stillness, identity, invariableness, immutability, arrestation, crystallization.
Focus. Center; standpoint; convergence, rendezvous, nucleus.
Ant. Circle, dispersion, divergence, dissipation.
Foggy. Misty, hazy; confused, dazed, bewildered, muddy, muddled; absent, stupid, obscure.
Ant. Alert, alive, awake; lucid, clear, bright; shrewd, sharp.
Foible. Frailty, weakness, failing, defect, imperfection, infirmity, fault, weak point; peccadillo.
Ant. Crime, atrocity, sin, enormity.