Usage: 8 forms in 14 verses
Form Translated As     In Verse(s)
συνέπεσον assembled for battle LXX.1Chr.14.9
συνέπεσεν it fell Luke.6.49
was not downcast LXX.1Sam.1.18
συνέπεσε are cast down LXX.Isa.64.11
became downcast LXX.Gen.4.5
downcast LXX.Gen.4.6
συνέπεσαν assembled for battle LXX.1Chr.14.13
met in battle LXX.2Sam.5.18
they met in battle LXX.2Sam.5.22
συμπεσούνται shall be cast down LXX.Isa.34.7
συμπεσείται shall be cast down LXX.Ezek.30.4
will be downcast LXX.Isa.3.5
συμπεσέτω be downcast LXX.1Sam.17.32
συμπέπτωκε cast down LXX.Isa.3.8

Liddell-Scott-Jones

συμπίπτω (sumpiptō) be downcast G:V

συμπίπτω,

Ionic dialect Iterat. συμπίπτεσκον [Refs 5th c.BC+]:—fall together, meet violently, of winds, σὺν δ᾽ Εὖρός τε Νότος τ᾽ ἔπεσον [Refs 8th c.BC+]; of two champions beginning to fight, fall to, fight hand to hand, σύν ῥ᾽ ἔπεσον [Refs 8th c.BC+]; ἐς νείκεα σ. [Refs 5th c.BC+]; of a hound, σὺν δὲ πεσών [Refs 3rd c.BC+]: with dative person, ξυμπεσὼν μόνος μόνοις [Refs 5th c.BC+]; of ships, λάβρῳ κλύδωνι σ. [Refs 5th c.BC+]

__2 generally, fall in with, meet with, especially with accidents or misfortunes, with dative of things, ἀσιτίῃσι [Refs 5th c.BC+]; but simply, fall in with, meet, τινι [Refs 2nd c.BC+]
__II of accidents, ailments, symptoms, events, fall upon, happen to, τοῖσιν αὐτουργίαι ξυμπέσωσιν μάταιοι [Refs 5th c.BC+]; ἀσθένεια, νοσήματα σ. τινί, [Refs 5th c.BC+]; συμπίπτει τοῖσι πλείστοισι τοιάδε· ἐρυθήματα προσώπου κτλ. [Refs 5th c.BC+]
__II.2 absolutely, happen, occur, τῆς αὐτῆς ἡμέρης συμπιπτούσης τοῦ τε ἐν Πλαταιῇσι καὶ τοῦ ἐν Μυκάλῃ.. τρώματος [Refs 5th c.BC+]; of heavenly bodies, coincide, [Refs 2nd c.AD+]
__II.3 with participle, like{τυγχάνω}, καὶ τόδε ἕτερον συνέπεσε γενόμενον [Refs 5th c.BC+]; but participle is sometimes omitted, ἐὰν ἴσοι συμπέσωσιν (i.e. ὄντες) [Refs 4th c.BC+]
__II.4 frequently impersonal or with neuter pronoun, it happens, comes to pass, followed by infinitive, τόδε σφι ὧδε συμπέπτωκε γίνεσθαι [Refs 5th c.BC+]; by ὥστε with infinitive, [Refs]; ξυνέπεσεν ἐς τοῦτο ἀνάγκης ὥστε.. matters came to such a pass that.., [Refs 5th c.BC+]infinitive, συνέπιπτε [αὐτὸν] ἀπῖχθαι [Refs 5th c.BC+]: with dative et infinitive, ὅσαις ἂν.. συμπέσῃ ἐμέσαι [Refs 4th c.BC+]; τὰ συμπίπτοντα one's lot or fortune, [Refs 5th c.BC+]; τὸ συμπεσόν the incident, [Refs 4th c.BC+]
__III coincide, agree or be in accordance with, σ. τούτοισι τόνδε τὸν λόγον [Refs 5th c.BC+]; ὥστε σ. τὸ πάθος τῷ χρηστηρίῳ turned out in accordance with it, [Refs]: absolutely, agree by chance, [Refs]; εἰς ταὐτὸν σ. agree in one, [Refs 5th c.BC+]; ἐμοὶ σὺ συμπέπτωκας ἐς ταὐτὸν λόγου have come to exactly the same point with me, [Refs 5th c.BC+]
__IV fall together, i.e. fall in, especially of a house, συμπίπτει στέγη [Refs 5th c.BC+]; φοβουμένη μὴ συμπέσῃ [τὸ ἰσιεῖον] [Refs 3rd c.BC+]; especially of the vessels of the body, fall in, collapse, [Refs 5th c.BC+]; μυκτῆρες συμπεπτωκότες, opposed to ἀναπεπταμένοι, [Refs 5th c.BC+]; σῶμα συμπεσόν a frame fallen in or emaciated, [Refs 5th c.BC+]; ὀφθαλμοὶ σ. [Refs 4th c.BC+]; of plant-structures, [Refs 4th c.BC+]; collapse, of animals, [Refs 3rd c.BC+]; of the heart, contract, [Refs 2nd c.AD+]; συνέπεσε τῷ προσώπῳ his face fell, [LXX]; τὸ πρόσωπον συνέπεσεν[LXX]; -πέπτωκα τῇ καρδίᾳ ἀπὸ μερίμνης[LXX]
__IV.2 σταφυλὴ λευκὴ συμπεπτωκυῖα dried grapes, [Refs 6th c.AD+]; πάντα δεδομένα κρέα συμπεπτωκότα ἔστω μέχρι δυοῖν ἡμερῶν hung, [Refs]
__V fall together, fall into the same line, σ. ἐπ᾽ ἀλλήλων ὑπὸ στενοχωρίας impinge one on another, [Refs 5th c.BC+]; converge, meet, τὸ τὰς παραλλήλους σ. οἴεσθαι [Refs 4th c.BC+]; οἱ πόροι παρ᾽ ἀλλήλους εἰσὶ καὶ οὐ σ. [Refs 4th c.BC+]; of the sides of a triangle, [Refs 2nd c.BC+]; of a river, σ. τῷ Κηφισῷ [Refs 1st c.AD+]

LSJ Scripture Refs: LXX.Gen.4.5LXX.1Kgs.1.18