Pyknós (πυκνός) means frequent, often, thick, dense. It describes regularity and intensity of practice. In the NT it appears in contexts of religious devotion and spiritual discipline.
Luke 5:33 contrasts the disciples of John and the Pharisees who fast 'often' (pykna) with Jesus' disciples who eat and drink. Jesus responds with the bridegroom metaphor — fasting will come when the bridegroom is taken away. In Acts 24:26, Felix 'frequently' sent for Paul, hoping for a bribe. First Timothy 5:23 uses it of Timothy's 'frequent ailments.' The word challenges us: what are we frequent about? Paul's command to 'pray without ceasing' (1 Thessalonians 5:17) calls for pyknos devotion — consistent, dense, unrelenting communion with God.