deep, close, thick, profound

deep, profound

unfaithfulness, infidelity, unchastity

undecided, to be determined, to be decided / (mathematics) indefinite; as in the term 'indefinite integral'

being undecided, being yet to be determined, or yet to be decided / (mathematics) indefiniteness, an integral being without specific limits

(grammar) infinitive

daring; fearless; intrepid; bold; tough

boldness, fearlessness, daring

irregular, occasional, unscheduled

irregularity