Felicitous, a.
Characterized by felicity; happy; prosperous; delightful; skilful; successful; happily applied or expressed; appropriate. Felicitous words and images. M. Arnold. -- Fe*lic"i*tous*ly, adv. -- Fe*lic"i*tous*ness, n.
Shades of meaning
Fernald has no entry of its own for felicitous; he lists it under happy.
Where he writes about it:
Happy is also applied to the ready dexterity or skill by which favorable results (usually in minor matters) are secured, when it becomes a synonym for dexterous, felicitous, and the associated words; as, he has a happy wit; happy at retort (compare clever). — from happy