(of feelings, behaviour etc) genuine; (of a person) not expressing feelings that are false
straightforward, honest
Cases of word usage
1) to ask (a person) with sincere and strong feeling (beg)
2) friendly and sincere (in feeling, behaviour) (cordial)
3) (of a person, what is said or how it is said) eager and fluent but not sincere (glib)
4) not sincere (insincere)
5) having, showing, sincere devotion to religion (pious)
6) thoughtful; not funny, silly or for pleasure; important because of danger; committed; sincere (serious)
7) the quality of being sincere (sincerity)