Greek: αδιαλειπτως [adialeiptôs] (Adverb). Incessantly, without ceasing. Assiduously.
αδιαλειπτως [adialeiptôs] appears 4 times in the NT:
(1) Romans 1: 9
For God is my witness, whom I serve with my spirit in the gospel of his Son, that without ceasing I make mention of you always in my prayers;
(2) 1 Thessalonians 1: 3
Remembering without ceasing your work of faith, and labour of love, and patience of hope in our Lord Jesus Christ, in the sight of God and our Father;
(3) 1 Thessalonians 2: 13
For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard of us, ye received [it] not [as] the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.
(4) 1 Thessalonians 5: 17
Pray without ceasing.